Geology Notes

What are minerals made up of?

• Elements

• ~92 Naturally occurring

What is an element?

• Matter that is made up of ATOMS that have the sane # of protons in the Nucleus

• Atoms are composed of three basic components

• Protons: a positively charged component of an atom found in the nucleus

• Electron: a negatively charged component of an atom found orbiting the nucleus

• Neutron: an atomic component with no charge found in the nucleus of an atom

• Element have different properties

How do we go from element to mineral

• 2 types of bonds:

• Ionic bonding: electrons are transferred between metals and nonmetals

• Covalent bonding: electrons shared between nonmetals

How do minerals form?

• Minerals form in 3 environments

• Precipitation from Aqueous solution

• Crystallization from magma

• Precipitation from organism

What is a Mineral?

• 5 characteristics that define a mineral

• Naturally occurring

• Inorganic

• Solid

• Definite chemical composition

• Internal structure of atoms

How can we tell them apart?

• Color:

• most obvious, but often misleading

• different colors result from impurities

• individual minerals, like quartz can be found in a variety of colors OR multiple minerals can share the same and/or similar color

• Streak:

• is a useful property that uses the color of a mineral in a powdered form. 

• Some minerals have specific streak colors that help identify them. 

• EX: Pyrite has a dark/grey/black streak colour

• however, streak is not exhibited by all minerals

• Luster:

• how a minerals surface reflects light. 

• Two major types: Metallic luster- looks like shiny metal such as chrome, steel, silver, or gold. Non-metallic luster: Doesn’t look like a metal and may be described as vitreous (glassy), earthy, silky, or pearly.

• Hardness:

• a mineral's resistance to scratching (most reliable). 

• Every mineral has a specific hardness. 

• Mohs scale of hardness: Hardest (10)-diamond, softest (1)- Talc. common objects: Fingernail(2.5), copper penny(3.5), wire nial (4.5), glass (5.5), streak plate (6.5)

• Cleavage: 

• Cleavage vs Fracture. The way a mineral breaks. 

• Cleavage: tendency of a mineral to break along pre-existing planes of weakness. T

• hese planes are created during the formation of the mineral. 

• Fracture: surface broken in various directions other than along cleavage planes, think how glass breaks. 

• Cleavage is not exhibited by all minerals

Other special properties

• Reaction with hydrochloric acid (calcite fizzes)

• Taste (halite tastes salty)

• Feel (Talc feels soapy, graphite feels greasy)

• Magnetism (magnetite attracts a magnet)

Mineral groups

• Group 1: Silicate minerals

• Rockforming minerals: ~30 common minerals make up most rocks in earth's crust

• Composed mainly of 8 elements that make up over 94% of the crust

• Group 2: nonsilicate minerals

• Resource bearing minerals: !6% of earth's crust

• Subclassified based on ions

How to build a silicate

• Silicates are built using a combination of the 8ost abundant elements in earths crust

• SI (silicons

• O (oxygen

• Mg magnesium

• Na sodium

• Fe iron

• Al aluminum

• K potassium

• These elements bond together to form a molecular ion called the silicon-oxygen tetrahedron.

• A tetrahedron has a pyramid-like shape with four sides and four corners

• 4 oxygen atoms covalently bonded to 1 silicon atom

Non silicate minerals

• Carbonetes CaCO32-

•  Calcite, dolomite, cement, chalk, antacids (TUMS

• Evaporates sulphates and halides (SO4)2-; Cl-, F-, Br-

• Halit =  table salt, de-icing roads

• Sylvite = sodium alternative

• Gypsum = drywall, constriction

• Oxides O2-

• Hematite, Magnetite

• Iron ores

• Sulphides S2-

• Galena: leas ore

• Sphalerite: zinc ore

• Chalcopyrite: copper ore

• Miscellaneous

• Flourite: smelting, metallurgy

• Corundum: jewelry, sandpaper

• Uraninite: uranium, nuclear power

• Native elements

• Copper, gold, silver, carbon

• Electronics, jewelry, writing

Polymorph

• Minerals with the same chemical composition BUT different internal arrangement of atoms. 

• EX: diamond and graphite

 Where does earth’s energy come from?

External heat engine

• The sun (nuclear fusion)

• Drives weather and climate, photosynthesis, weathering/erosion. etc

Internal heat engine

• Earths core (remnant heta + radioactive decay)

• Responsible for formation of minerals and (most) rocks

• Power forces that generate earthquakes, volcanoes, and mountain building events

What is a rock?

In essence, a rock is a solid aggregate (combination) of one or more minerals

Types of rocks

• Igneous: 

• Sedimentary

• Metamorphic

Why do we care?

Volcano behavior

• Magma composition affects whether eruptions are explosive (rhylitic) or gentle (basaltic)

Rock formation

• Determine igneous rocks like basalt, andesite, granite

Hazards and resources

• Predicting eruptions, locating mineral deposits (e.g. copper in evolved magmas)

Geologic insight

• Helps geologists interpret plate boundaries and earth's interior

What is magma and how does it form?

Magma - molten rock beneath the earth;s surface, containing liquid, crystals, and gases.

• It's the source of all igneous rocks, which are a fundamental part of the rock cycle

There are 3 primary ways solid rock turns into magma:

• Decompression melting: primarily at divergent plate boundaries (like mid-ocean ridges, where plates pull apart) and hotspots (like Hawaii where mantle pilates rise)

• Flux melting: exclusively at convergent plate boundaries where subduction occurs

• Heat transfer melting: often occurs in the continental crust where magma chambers form or where hot mantle plates interact with the base of the crust.

Magma vs Lava. What’s the difference?

• Molten material at and/or near the surface = Lava. Cools over minutes, days, or even months

• Molten material below the surface = magma. Cools slowly over millions of years

Igneous processes

• On earth's surface: volcanic igneous rocks = AKA Extrusive Igneous rocks. 

• Named after vulcan the roman god of fire

• Lava and ash flow along the earth surface and crystalize

• Spreading centers, continental volcanoes, and oceanic island arcs (e.g. iceland, Mt. Vesuvius, Japan, Hawaii

• Below the earths surface: Plutonic igneous rocks = Intrusive igneous rocks

• Named after Pluto, the roman god of the underworld

• Magma cools and crystalizes underground

• Brought to the surface via uplift/erosion (ex. Yosemite, Mt. Rushmore)

Identifying Igneous rocks

• Texture: the “texture” of an igneous rock describes the size of mineral crystals found in an igneous rock that directly relates to its rate of cooling. 

• Two main textures. Phaneritic. Aphantic: Special textures: Vesicular, glassy, pyroclastic, porphyritic

• Phaneritic Texture: individual minerals can be seen with the naked eye. Cooled slowly somewhere deep beneath Earth's surface

• Aphanitic Texture: individual minerals cannot be seen without a microscope or hand lens. Cooled rapidly as molten rock is brought quickly to earth’s surface during a volcanic eruption and exposed to the elements

• Vesicular texture: preserved voids or vesicles that form from volcanic gasses escaping and rapidly cooling to for fossilized bubbles

• Glassy Texture: forms when silica-rich lava erupts rapidly from a volcano. It cools so quickly that no minerals can form, resulting in the formation of volcanic glass

• Pyroclastic texture: describes igneous rocks that are made up of pyroclastic material such as ash, cinders, bombs, etc…pyroclastic material cools extremely quickly so minerals have no chance to grow

• Porphyritic texture: igneous texture that indicates a shift in conditions within a magma chamber. Exhibits two distinct sizes of mineral crystals

• Composition

• Mineralogical makeup of the rock

• 2 categories of silicate minerals tha affect the composition of igneous rocks: Light silicate: quartz, feldspars, micas. Dark silicates (ferromags): Olivine, pyroxene hornblende

• Browns reaction series: igneous minerals follow a trend in composition and temperature at which minerals crystalize when cooled

How magma evolves: Partial melting

• When a rock melts, it doesn't all melt at once

• Minerals have different melting points. Minerals with higher silica content melt at lower temperatures, while lower silica mafic materials melt at higher temperatures

• The melt produced is typically more felsic (silica-rich, lighter in color) than the original source rock, leaving behind a more mafic, unmelted solid

Fractional crystalization

• As magma cools, minerals crystalize out of the melt at different temperatures

• Denser, higher-temperature minerals (ex. olivine) crystalize first often sink, removing their components from the remaining melt

• The remaining liquid magma becomes progressively more felsic (enriched in silica, aluminum, sodium, and potassium) as mafic minerals are removed

Magma mixing and assimilation

• Magma mixing: two distinct magma bodies, often with different compositions, can come into contact and mic. 

• This can happen when a new batch of magma intrudes an existing magma chamber

• The two magmas blend to form a new, intermediate composition

• Assimilation: as magma rises through the crust it can melt and incorporate surrounding country rock

• The incorporated rock changes the overall chemical composition of the magma

• The magma becomes contaminated, altering its composition toward that of the assimilated rock

Igneous compositions

• 3 chemical compositions: Felsic = lighter color. Mafic = darker color. Intermediate = mix of light and dark color

• Special composition: Ultramafic: ~90% ferromagnesian, mostly composed of the mineral Olivine

Why bother with composition?

• Provides insight into WHERE the igneous rock formed

• Felsic and intermediate: convergent plate boundary, continents

• Mafic: spreading centers, hotspots, normal faults

• Ultramafic: mantle-derived, deep underground

Why are Sedimentary rocks important?

• Make up the largest percentage of rocks on earth's surfaces

• Sedimentary rocks are the only rocks that contain fossils

• Sedimentary rocks have the unique capacity to preserve evidence of past environments

• Sedimentary rocks act as an important source of rock for a variety of natural sources (e.g. potable water (groundwater), oil/petroleum, and natural gas

Types of sedimentary rocks

• Clastic: sediment (residue material that is not dissolved by chemical weathering) is deposited and lithified. Weathering: The physical and/or chemical breakdown of rocks via mass wasting, size: boulder, gravel, sand, and mud, shape: angular or rounded. Erosion: movement of sediment from its source, wind, water, and gravity, as sediment is eroded further from its source area, its size reduces, and its shape becomes more rounded. Deposition: where the eroded sediment/material finally comes to a stop. Lithification: accumulation of sediment (compactation) squeezes out the air and water, which becomes replaced by fluids with ions that crystallize, cementing (cementation) the particles together

• Chemical: form from ions crystallizing from water

• biogenic/bioclastic: involves the remains of plants and/or animals

What does the shape of the sediment tell you about how far it was transported?

• Round clasts = traveled far distance

• Angular clasts = traveled short distance

Chemical sedimentary rocks

• Form via the precipitation of minerals from an aqueous solution

• Two types, evaporite: form from a saline (salty) solution that evaporates, leaving behind a mineral precipitate (e.g. rock salt and rock gypsum. Limestones: precipitation of calcite out of groundwater in caves or from shallow warm seas

Biogenic sedimentary rocks

• Are composed of the remains of plants or marine organisms

• Two groups. Organic and Biochemical

• Coal: a carbon-rich rock created as buried plant matter is chemically altered by deep prolonged heat and pressure. The presence of coal represents an ancient swamp environment

• Limestones: made from the shells of marine organisms - usually form in shallow waters

What is a Metamorphic rock?

Rocks that are altered due to various tectonic forces

To create a metamorphic rock, we must first start with a protolith or parent rock (shale - schist)

3 agents or metamorphism

Fluids, temperature, and pressure

Temperature

How can we increase the temperature of a rock?

• Increase its depth into the crust via burial

• Interact with a body of molten material

Pressure

2 types of pressure/stress

• Lithostatic pressure AKA Uniform stress
  - pressure that is distributed equally from all directions
  - pressures increase with depth due to weight of overlying rocks

• Directed pressure AKA Non-uniform stress
  - pressure tat being ‘applied” from two directions
  - similar to pressing your palms together

Fluids 

• There are fluids found in all rocks in the form of hydrous minerals

• During metamorphism, these fluids act as a catalyst in altering minerals in the protolith into new metamorphic minerals

• However, at greater depths, fluids in rocks also assist in melting rock

Metamorphic environments

• Metamorphic rocks form in 2 distinct metamorphic environments that affect the type of metamorphic rock created

 -Contact metamorphism

 -Regional metamorphism

Contact metamorphism

• Results from the “contact” between a rising body of magma and the surrounding parent/country rock

-results in the parent/country rock being “baked” into a new metamorphic rock

• Pressure/temperature trend
  - pressure = low
  - Temperature = high

Regional metamorphism

• Results from the convergence or collision of two tectonic plates
  - results in the parent/country rock being squeezed and sheared in 2 directions

• Pressure/Temperature tren
  - pressure = high
  - Temperature - low to high

Identifying metamorphic rocks

• Metamorphic rocks are categorized based on the ‘texture’ that results frim the metamorphic environment they form in
  - Foliated has “layers”
  - Non-foliated doesn’t have “layers

Foliated

What is foliation?

• Alignment of mineral crystals parallel to the direction of directed pressure

Which metamorphic environment would this form in?

• Regional metamorphism

Slate - flat full layers. Protolith - shale. Fine-grained and dull luster

Phyllite - wavy, shiny layers. Protolith - slate. Fine-grained and subtle gloss/shine

Schist - wavy layers w/ visible platy minerals. Protolith - phyllite. Coarse-grained, shiny, and flaky

Gneiss - alternating layers of dark and light minerals. Protolith - schist or granite or diorite. Coarse-grained, parallel light and dark bonds/layers

Non-foliated

• Dependent on type of parent rock that is “baked” and recrystallized

Which metamorphic environment would this form in

• Contact metamorphism

Quartzite

• Protolith: quartz-rich sandstone

• Mineral composition: quartz

• Properties: hard, scratches glass, can be any color, and does not react to acid

Marble

• Protolith: limestone

• Mineral composition: calcite

• Properties: won’t scratch glass, can be any color, and reacts to acid

Serpentinite

• Protolith: ultramafic igneous rock (e.g. peridotite)

• Mineral composition: antigorite, chrysotile, and lizardite

• Properties: greasy or silky luster, and can appear scaly (like snake skin). Source of Asbestos

Amphibolite

• Protolith: Mafic igneous rocks (e.g basalt or gabbro)

• Mineral composition: Amphibole and plagioclase

• Properties: resembles a mafic phaneritic igneous rock

Hornfels 

• Protolith: basalt

• Mineral composition: hornblende and pyroxene

• Properties: often appears similar to a aphanitic mafic igneous rock

Anthracite

• Protolith: bituminous coal

• Mineral composition: carbon

• Properties: black to steel gray color, conchoidal fracture, and semi-metallic luster

Plate Tectonics

What is the scientific method?

• A structured process used by scientists to investigate observations and answer questions about the natural world

• Its a systematic, logical, and repeatable process. It is a cycle, not a straight line

Step 1: Observation

• All scientific inquiry begins with an observation that leads to a question

Step 2: Hypothesis

• A hypothesis is a testable statement or proposed explanation for an observation

Step 3: Experiment

• This is where you design and conduct an experiment to test your hypothesis.
  - Independent variable: the factor you change
  - Dependent variable: the factor you measure
  - Controlled variable: factors you keep constant

Step 4: Analysis

• After the experiment, you organize and analyze the dfata you collected

• Look for patterns, trends, and relationships
  - Use charts, graphs, or tables

Step 5: Conclusion

• Based on your data analysis, you determine whether uout hypothesis was supported r not

• The goal is to prove or disprove the hypothesis, not just get the “right” answer

Why it matters

• The scientific method is crucial for advancing human knowledge and solving problems

• It helps us to
  - avoid bias and superstition
  - create reliable knowledge
  - develop new technologies and medicines

Earth’s Interior

• Earths interior consists of 3 main layers
  - crust
  - mantle
  - core

Earth’s Interior: Crust

• Broken into large pieces called plates

• 2 types of plates:

• Continental plate
  - thick: 35-70 km in thickness
  - Low density: 2.7g/cm3
  - Old: average age = 3.5 billion years old
  - Made of granite

• Oceanic plate
  - thin: 3-15 km in thickness
  - high density: 3.0g/cm3
  - young: none older than 180 million years old
  - made of basalt
  
  

Earth’s Interior: Mantle

• ~2900 km thick

• It makes up 82% of Earth’s volume

• Made of the upper and lower mantle
  - the lower mantle is pretty mysterious, while the upper mantle is better understood

• The upper mantle consists of 2 layers:

• Lithosphere
  - solid, rigid rock
  - includes the crust

• Asthenosphere
  - solid rock, but under high pressure
  - Similar to taffy

Earth’s Interior: Core

• About 3500 km in radius

• Made mostly of iron (and a little nickel

• HOT!!: about 7000 degrees celsius

• Made of 2 layers:

• Inner core
  - solid
  Higher composition nickel

• Outer core
  - molten
  - higher composition iron

Isostacy

• The plates float on top of the mantle
  - Dense and thin oceanic plates sink a little lower into the asthenosphere
  - less dense and thick continental plates float a little higher on the asthenosphere

• This concept of “floating” plates is called isostacy

Before the Theory:

In 1912, a German meteorologist, geophysicist, and polar researcher by the name of Alfred Wegener introduced a highly controversial concept in the realm of earth science

Hypothesis of Continental Drift:

Hypothesis that proposed that all of Earth’s continents were once houned in one large supercontinent called “Pangea”

Too good to be true?

Though a solid hypothesis, Wegener’s proposed supercontinent was largely dismissed as at the time other scientists supported the idea that earth’s continents and ocena basis were fixed

Wegener used 4 key “evidence” to support his hypothesis of continental drift

1. Continents fit like puzzle pieces
   - edges of continental margins, especially those of south America and Africa fit together like “puzzle pieces”

2. Matching geologic units and mountain ranges
   - distinctive belts of rock occur in both south america and africa
   - Wegener also noted that mountain ranges in North America would connect with mountain ranges in Africa, Greenland, Great Britain, and Scandinavia is the continents were joined

3. Matching paleoclimate belts
   - rocks preserve evidence of ancient climates
   - Limestone = warm shallow seas
   - Coal = swamps
   - Crossebedded sandstone = deserts and dunes
   - Laterite (iron rich soil/rock) = tropical rainforest
   - Glacial striatations and Till - glaciers
   - Paleoclimates align when Pangea is reconstructed

4. Matching fossils
   - Mesozoic fossils of the same species are found on many southern continents today
   - Mesosaurus - freshwater reptile.These creatures could not migrate across an ocean
   - Glossopteris - tropical fern
   - Where was this fossil found and why was it confusing
   - Finding these fossils where no present-day tropical environment

• Despite all of Wegener;s evidence supporting his hypothesis, continental drift was largely rejected. 

• Wegener lacked a credible mechanism (driving force) that explained how and/or why the continents moved. 

• Wegener suggested that gravitational pull from the sun and moon may be capable of moving the continents, like the tides

• Wgener’s idea languished for several decades after his untimely death in Greenland in 1930

• However, major scientific advances in the 1940’s, 1950’s, and 1960’s brought Wegener’s idea back to life

• Scientific advancement during the 1940s provided some new evidence
  - WWII = military spending

• U.S. Navy accidentally mapped the seafloor while trying to find the hidden enemy German U-boats in the Atlantic

Sea-floor spreading

• Before the 1950s
  - very little was known about the structure of the ocean floor
  - ocean basins were thought to be featureless

• In 1952, a geologist and oceanopraphic cartographer by the name of Marie Tharp produced the first scientific map of the Atlantic ocean floor
  - used sounding profile data to create 6 bathymetric profiles of the North Atlantic
  - discovered the mid-atlantic ridge

• Dating of rocks using radioactivity (radiometric dating) was another scientific advance of the 1950-60’s
  - before this, rocks were dated using fossils and the exact age of the rock was unknown

• Radiometric dating revealed 2 interesting things:
  - average age of the continents is 3.5 billion years old
  - oldest ocean rock is 180 million years olf
  - ocean floor rocks are new at mid-ocean ridges and get older the further you get from the ridge

• Harry heiss, a geologist from princeton university
  - tried to explain the advances in seafloor mapping, and the radiometric dates of the seafloor by proposing his idea of “seafloor spreading” in 1962
  - his idea painted mid-ocean ridges as giant cracks in the earth’s crust being pulled as the ocean spreads apart
  - As the cracks open, magma comes up from below ad fills the crack, making new seafloor when it solidifies
  - More magma is added to teh crack constantly, so new rock is added to the ocean crust all the time

• This idea, therefore, implies that the oceans (as well as the earth) are constantly getting larger as more rock is added

• Is it possible for the earth to get bigger
  - No, the earth cannot get any larger
  - As a result, Heiss’ idea was rejected

Paleo-magnetism

• In the 50s and 60s, scientists studying past magnetic fields (paleomagnetism) realized earth’s magnetic field is surprisingly erratic
  - Poles don’t align: Magnetic north does not sit at the geographic north pole
  - Magnetic north wonders: the google constantly drifts over time
  - Poles reverse: every ~500,000 years on average, magnetic north and south completely flip

• In the 1950s, scientists discovered that Earth’s magnetic strength varies by location:
  - Positive anomalies (Orange/Red bands):
  - Negative anomalies (White bands):

- Formed when the magnetic field was normal, adding to Earth's current
field strength.

Formed when the magnetic field was reversed, canceling out some of
Earth's current field strength.

• Continuous creation and movement:
  - New seafloor constantly forms at mid-ocean ridges and carries older crust
  outward in both directions.
  - This process leaves identical, mirror-image bands of magnetic anomalies on
  either side of the ridge.

• Proof of seafloor spreading:
  - These matching stripes provided the direct evidence confirming Harry Hess’s
  idea of seafloor spreading.

• Proposed in the late 60s-70s:
  - Geology's unifying model showing Earth’s rigid outer shell (lithosphere) is
  broken into moving plates floating on the mantle.

• Driving Forces:

• Mantle Convection:

• Hot material rises toward the crust, cools, and sinks back toward the core,
  cycling like a conveyor belt.

• Ridge-Push & Slab-Pull:

• Gravity slides plates down from elevated mid-ocean ridges (ridge-push) and
  dense, cold slabs sink into the mantle, dragging plates behind them (slab-
  pull).

• Introduction of Plate Boundaries:

• The movement of these plates triggers major geologic events:

• earthquakes, volcanoes, and mountain building.

• 3 types of boundaries = 3 types of plate motion
  - convergent boundary
  - divergent boundary
  - Transform boundary

• Convergent boundary
  - Two plates coming together (converging), as one plate is either subducted underneath another or colliding with another plate.
  - volcanoes and earthquakes are a common by-product of convergent boundaries (e.g. the Ring of Fire)
  - Convergent boundaries are also sub- categorized into one of three convergent types:

• Oceanic-Continental

• Oceanic-Oceanic

• Continental-Continental

Oceanic continental

• Oceanic crust that is being subducted beneath Continental crust

• Subduction here leads to the formation of Volcanic Mountains.

• e.g. Andes Mountains, Mt Shasta,
  Mt Rainier, Mt Saint Helens

Oceanic-oceanic

• Oceanic crust that is being subducted beneath Oceanic crust

• e.g. Japan, the Aleutian Islands (Alaska), The Philippines

• Subduction here leads to the formation of Volcanic Island Arc.

Continental-continental

• Continental crust "collides with another slab of Continental crust

• No subduction, so we do not generate volcanoes.

• Instead, the plates crash into each other like a deck of cards and form what we call "highly folded mountains"

• e.g. The Himalayas and the Alps

Divergent Boundary

• Plates are drifting ot diverging part from each other

• As they drift apart, molten material comes to the surface, creating new oceanic crust

• There are technically two types of divergent boundaries
  - Mid-ocean rifting. Mid-atlantic ridge
  - Continental rifting. East african rift valley

Transform boundary

• Commonly known as “stress release zones”

• Here plates move horizontally passed each other

• Though they are still capable of generating earthquakes, there is no subduction or mantle upwelling to generate material to create volcanoes

Earthquakes

What is an earthquake?

• Shaking at Earth’s surface caused by the sudden and rapid release of energy within the crust

Principle of elastic deformation

• Tectonic forces cause stress that builds up in rock over time.

• The rock bends and deforms like a rubber band, storing energy

• this stress is a type of potential energy

Shaking around the world

• Are there any observable trends of where earthquakes occur

• Occur where two tectonic plates interact

Components of a seismic event

• Foreshocks: smaller quakes that precede the main shock

• Main shock: the largest earthquake in the sequence

• Aftershock: smaller quakes that follow the main shock adjusting to the new stress

Anatomy of an earthquake

• Epicenter: the point/area on the Earth’s surface that is directly above the focus

• Rupture Surface: fault plane that slips during an earthquake.

• The size of the rupture surface is a key factor in determining the earthquake's magnitude.

• Focus/Hypocenter: the point/area at depth (within the crust) where the earthquakes/shaking originated from

Deep v. Shallow earthquakes

• Shallow earthquakes shown in hotter colors

• Deeper earthquakes shown in cooler colors

Episodic Tremor and Slip (ETS)

• ETS is a slow, gradual release of stress deep within a subduction zone.

• Movement on one part of a fault can increase stress on other parts, leading to more quakes.

• Movement on one part of a fault can increase stress on other parts, leading to more quakes.

• ETS events can increase stress on the locked, upper part of a subduction zone.

• This process is thought to contribute to the buildup of energy for very large
  megathrust earthquakes.

• This process is thought to contribute to the buildup of energy for very large megathrust earthquakes.

Earthquakes and plate boundaries: convergent boundaries

• Megathrust Earthquakes
  - subduction zomes produce powerful megathrust earthquakes on the interface between two plates, causing widespread destruction

• Cascadia subduction zone
  - The cascadia subsuction xome is a locked fault off north america capable of producing a magnitude 9 earthquake

• Continental collision zome
  - collision of two continental plates causes crust uplift. Thickening, and formation of thrust faults and folds

• Himilayas formation
  - the himalayas formation formed from the Indian and eurasian plate collision, exemplifying seismic activity from continental collision

Earthquakes and plate boundaries: divergent boundaries

• Characteristics of divergent quakes
  - earthquakes at divergent boundaries are generally small, shallow, and less hazardous to humans

• Intraplate earthquakes
  - intraplate earthquakes occur within tectonic plates and can be highly damaging despite their rarity

Earthquakes and plate boundaries: transform boundaries

• Transform plate boundaries
  - Transform boundaries occur where plates slide horizontally, causing large, shallow, and destructuve earthquakes

• San Andreas Fault
  - The San Andreas Fault is a major transform between the Pacific and North American plates causing frequent earthquakes

But where are earthquakes generated?

• Faults
  - fractures in the earths crust where earthquakes occur
  - all faults generate earthquakes

• Three types of faults
  - Normal Fault
  - Reverse Fault
  - Strike-slip Fault

Normal Faults

• Move due to extensional forves pulling blocks apart

• Have vertical displacement where the hanging wall falls in comparison to the foot wall

Reverse faults

• Reverse faults move due to compressional forces pushing blocks together 

• Reverse faults have vertical displacement where the hanging wall moves up in comparison to the foot wall

Strike-slip faults

• Strike slip faults move due to shear forces which move the block past each other horizontally

• There is no vertical displacement

• No hanging wall or footwall

• There are two types of strike-slip faults:
  - Right-lateral
  - Left-lateral

What’s the fault?

• Is this a wall or aerial view? Aerial view

• Is there a footwall or hanging wall? No

• What type of fault is this? Strike-slip, right-lateral

What’s the fault?

• Is this a wall or aerial view? wall

• Is there a footwall or hanging wall? Yes

• Did HW move up or down? down

• What type of fault is this? Normal fault

What’s the fault?

• Is this a wall or aerial view? wall

• Is there a footwall or hanging wall? Yes

• Did HW move up or down? up

• What type of fault is this? Reverse fault

What kind of faults do we have in California?

• The San Andreas Fault
  - right-lateral strike-strike-fault
  - major concerns for californians

How do earthquakes move?

• Energy released when a fault ruptures (an earthquake) travels through our planet in the form of several different ‘waves’

Body waves

• Seismic waves that travel through earth’s interior

• Two types of body waves
  - P(primary)-waves: compression waves, travel teh fastest and can travel through any state of matter (solid, liquid, or gas)
  - S(secondary)-waves: shear waves, second fastest waves, and can only travel through solids

Sueface waves

• Travel more slowly and will only travel through the earth’s crust

• Most of the “shaking” that we feel during an earthquake is due to the combination of the two types of surface waves

• Two types of surface waves
  - L-waves (Love waves) move in a rolling zig-zag motion
  - R-waves (Rayleigh waves) move in a rolling “water wave” motion

Predicting earthquakes?

• Short term prediction
  - not entirely possible just yet

• Long term prediction
  - Faults tend to have earthquakes that recur often
  - The probability of a quake over an extended period can be estimated based on how long it has been since the last quake (example: On average, the San Andreas fault has a large earthquake every ~150 years. The last major earthquake occurred ~300 years ago)
  Seismologists estimate that there is a 99% probability of a major earthquake within the next 30 years

Detecting and measuring earthquakes

• Earthquakes are measured on a scale called the Richter scale (one being the weakest and ten being the strongest). The power of the earthquake is measured using a machine called a seismometer

• Certain apps receive warning of an earthquake before you feel shaking

• USGS Quakes report ‘feeling’ an earthquake via their Did You Feel It? Web page

• Seismograms give us two big details about an earthquake:
  - The size of the earthquake; larger surface waves means larger earthquake
  - how far away it happened by observing the difference in arrival of P-wave and S-wave

Looking for the Epicenter of an Earthquake

• Locating the epicenter of an earthquake is done using a princess call Triangulation
  - Need at least 3 seismographs in different locations (seismic stations)
  - Look at the difference of arrival time of P-waves, and S-waves for each seismograph
  - Use that difference in arrival time to plot the approximate distance each seismic station from the epicenter
  - Where these plots meet is the location of the epicenter of the earthquake

Detecting and measuring earthquakes

• Earthquake magnitude measure the energy released at the source of the earthquake via a single objective number for a given seismic event
  - Richter Scale: It is a logarithmic scale, with each whole number increase representing a 10-fold increase in seismic wave amplitude
  - Moment Magnitude Scale: It is a modern standard for measuring large earthquakes. It is based on the seismic moment, which is a more accurate measure of the total energy released

• How the scale works: an increase of one whole number in magnitude corresponds to a tenfold (10^x) increase in the amplitude of the seismic waves measured on a seismogram

• Earthquake intensity measures the amount of shaking and damage at a particular location. It varies with distance from the epicenter, local geology, and building construction.

• Modified Mercalli Intensity (MMI) Scale
  - It is a qualitative scale based on observations of damage and human perception
  - It ranges from I (not felt) to XII (catastrophic destruction)

Building vs Vibrations

• Shaking during an earthquake can be any combination of up and down , and side to side, in any direction

• Lack of proper reinforcement, poor materials and outdated designs are common factors

• Modern building codes are designed to make buildings resistant to seismic shaking, as they require steel reinforcement, flexible foundations, and other features to absorb energy

• To mitigate damage, engineers have designed buildings to be able to flex and sway without becoming unstable

• Flexible buildings in Tokyo saved many lives during the M 9.0 earthquake that shook Japan in 2011

Amplification of Seismic Waves

• Underlying rock types within an area have the capability of increasing or decreasing the amount of shaking during an earthquake

• Areas with solid rock foundations (such as mountainous regions) tend to dampen seismic waves
  - rock transits seismic energy quickly, with less amplification

• Areas with loose sediment foundations (such as LA and Orange County) will feel amplified shaking
  - unconsolidated sediments and soft soils can magnify

Liquifaction

• A process where water-saturated, unconsolidated sediment loses its strength and stiffness. 

• The ground behaves like a fluid, and buildings can sink or tilt

• How liquefaction happens
  - Shaking increases the pressure of the water in the pore spaces of the sediment
  - This pressure pushes the grains apart, reducing the strength of the ground.

Tsunamis

• A tsunami is a large wave or series of waves caused by the displacement of a large volume of water.
  - Most tsunamis are caused by a large undersea earthquake

• How an earthquake generates a Tsunami
  - A large thrust earthquake on a subduction zone displaces the seafloor vertically
  - This movement displaces the entire column of water above it,
  - The energy travels across the ocean as a tsunami

• Warning system:
  - The U.S. Coast and Geodetic Survey established a tsunami warning system for coastal areas of the pacific  after the 1946 Tsunami in Hawaii
  - A warning system was established in the Indian Ocean after the 2004 Tsunami
  - Warning system for the North-east Atlantic and Mediterranean in 2005
  - A warning system for the Caribbean was completed in 2010

Slope failure (Landslides)

• The shaking destabilizes slopes that may already be weak

• This can cause widespread damage, especially in hilly or mountainous regions

• Most damage in the 1964 Alaskan Earthquake was from landslides

Fires

• Fires are a common secondary hazard of earthquakes

• Shaking can rupture gas lines, create electrical shorts, and topple power lines
  - may cause more destruction than the earthquake itself

• Broken water mains can hinder firefighting efforts

Volcanoes

What is Volcanism?

• Volcanism is the process where magma and gases come to the Earth’s surface 

• A volcano is the landform that builds up from repeated eruptions at a single location

• Eruptions can occur on land or underwater 

Volcanic settings

• Three primary tectonic settings where volcanism occurs
  - Divergent Plate Boundaries (Mid-Ocean Ridges)
  - Mantle Plumes (Hot Spots)
  - Convergent Boundaries (Subduction Zones)

Volcanism at Divergent Boundaries

• Divergent boundaries (like mid-ocean ridges) are where plates move apart

• Mantle rock melts as it rises and loses pressure
  - This forms mafic (basaltic) magma

Volcanism at Convergent Boundaries

• Subduction zones are where one plate descends beneath another

• Water from the sinking plate helps the mantle rock above it melts
  - this forms Rhyolitic or Andesitic (felsic) magmas

Volcanism at Hot Spots

• Hot spots are areas where mantle plumes rise form deep within the mantle

• Melting occurs as the plume reaches the lithosphere

• The plume is stationary, while the plate moves over it
  - creates a chain of volcanoes

Magma Properties: Viscosity

• Viscosity is a fluid’s resistance to flow (thicker fluid = more viscous)

• Influenced by temperature and chemistry

• Temperature
  - high temp = low viscosity (runny)
  - low temps = high viscosity (thick)

• Chemistry
  - low SiO2 = low viscosity (runny
            - mafic magmas
  - high SiO2 = high viscosity (thick)
              - felsic magmas

• Aa: jagged and angular - lava is cooler and has a lots and lots of gas

• Pahoehoe: ropey and more fluid

Magma Properties: Dissolved Gases

• The build-up of volcanic gases provides the force to eject magma/lava from the volcano
  - as magma rises, the pressure decreases, and the gases begin to form bubbles
        - how a soda fizzes when opened
  - gas bubbles cannot form in magma deep within the crust due to the high pressure

Explosive vs Non-Explosive Eruptions

• Explosive eruptions are characterized by violent explosions

• They occur with magmas that have high viscosity and high gas content
  - gasses get trapped, pressure builds up, and the eruption is violent

• Hunga Tonga-Hunga Ha’apai eruption
  - January 15, 2022
  - largest underwater explosion ever recorded.
  - produced a 60 megaton explosion that was x4,000 bigger than hiroshima

• Non-explosive eruptions are characterized by gentle lava flows.

• They occur with magmas that have low viscosity and low gas content
  - the gases can escape easily, preventing pressure buildup

Types of eruptions

• Hawaiian-style eruptions (non-explosive) are linked to basaltic magma

• Case study: Kilauea Volcano
  - frequent, non-explosive eruptions
  - characterized by flowing lava streams

• Plinian-style eruptions (explosive)

• Case study: Mount St. Helens
  - 1980 explosive eruption
  - a classic example of a Plinian-style eruption

Active, Dormant, or Extinct?

• Common words used to describe the level of “activity” that a volcano exhibits

• Active
  - currently erupting or has erupted within the last 10,000 years

• Dormant
  - has not erupted in the last 10,000 years but shows evidence of unrest (earthquakes, gas emissions, etc…)

• Extinct
  - last eruption occurred more than 10,000 years ago and shows no evidence to support a future eruption

Shield volcanoes

• They have broad, gentle slopes, resembling a warrior's shield.

• Built from repeated eruptions of low-viscosity basaltic lava

• low viscosity magma, low gas content, and non-explosive eruptions.

• lava flows travel long distances.

• Typically form at hot spots and mid-ocean ridges.

• Case Study: Mauna Loa

• It is the largest active volcano on Earth, located in Hawaii.

Composite (strato) Volcanoes

• They are steep-sided, symmetrical cones.

• Built from alternating layers of lava flows and pyroclastic material.

• high-viscosity magma, high gas
  content, and explosive eruptions.

• lava flows are short and
  chunky.

• Typically found at subduction zones.

• Case Study: Mount Fuji

• classic example of a strato volcano.

• It is located on a subduction zone and has a beautiful, iconic cone shape.

• Mt Vesuvius, Italy
  - Last major eruption in 1944
  - Made famous for its eruption in 79 AD for the destruction of the city of Pompeii

Cinder cone Volcanoes

• Steep conical hills that can reach heights of 3,000 m..

• A common volcanic landform
  - forms on slopes of shield or caldera volcanoes
  - made of cinders (a type of pyroclastic material)

• Case Study:Volcán Paricutín, Michoacán, México

• began erupting in Feb 1943

• grew to 165ft in 24 hrs

• dormant since 1952

• total height: 1,391ft

Plug Dome Volcanoes

• Plug domes are a feature of high-viscosity Magma.

• Lava is too thick to flow, builds up on itself (forming a plug), and seals the vent as a result

Caldera

• It occurs when the summit of a volcano collapses into its magma chamber after a major eruption

• formed ~7,700 years ago after summit collapse of Mount Mazama Strato-volcano

• Case Study: Crater Lake

• Forms a crater that is > 1 km in diameter

Long valley Caldera, CA

• Formed ~760,000 years ago

• Is classified as an ancient super volcano
  - erupted 600 km^3 (140 mi^3) of pyroclastic material

Flood Basalts

• Occurs when magma surges up through massive cracks in the Earth's crust, spreading across a vast area.

• Colombia River Flood Basalts:

• erupted between 17.5 and 6 million years ago

• 5 eruptions

• ~16,000ft thick

Lahars

• a type of mudflow composed of volcanic debris and water.

• 2 main triggers:

• Rapid melting of snow and ice during an eruption.

• Intense rainfall on loose volcanic deposits.

Pyroclastic flows:

• Fast-moving cloud of super heated gas, ash, and rock fragments.

• They are extremely dangerous and can reach speeds of up to 430 mph.

• They are extremely hot (up to 1,000∘C) and can cause instant death.

• They can potentially flow out to 90 miles away

The Hydrologic Cycle: Rivers

The Hydrologic Cycle

• What is the primary source of energy for the Hydrologic cycle?
  - the sun

• Phases of the Hydrologic Cycle:
  - Evaporation: Solar energy is absorbed by bodies of water then turned into water vapor
  - Condensation: water vapor rises and cools to form clouds
  - Precipitation: clouds become saturated and return water back to the surface

• Water on the surface can take several paths:
  - runoff through rivers
  - infiltration as groundwater
  - transpiration through trees/plants

What is a river?

• A body of running water confined to a channel, that runs/flows downhill in response to gravity

• Where a river/stream starts is known as the head or source

• Where a river/stream empties or ends is known as the mouth

Parts of a river

• Channel: long depression eroded by a stream into rock or sediment

• V-shaped channel vs U-shaped channel
  - shape dependent on velocity of water

• Stream bank: the terrain alongside the bed of a river (the sides of the river) 

• Stream bed: the channel bottom of a stream or river

Notable rivers

• Nile river: world longest flowing river, flows through 11 African countries
  - Burundi
  - Rwanda
  - Tanzinia
  - Kenya
  - Democratic Republic of the Congo
  - Uganda
  - Ethiopia
  - South Sudan
  - Sudan
  - Egypt

• Amazon river: the highest discharge of freshwater

• Huong He (yellow) River (Asia): ‘yellow’ due to the high amount of sediment load being transported

Drainage basin

• The total areas that is ‘drained’ by  a stream/river and its tributaries

• Tributary: smaller streams that ‘feed’ into the main river
  - Missouri river

• Divide: the elevated boundary separating areas that are drained by different river systems
  - What are the divides for the Mississippi river? Rocky mountains and appalachian mountains

3 roles of a river:

1. Erosion

2. Transportation

3. Deposition

• The role is determined by the velocity of the water
  - when velocity decreases, which role is more prevalent?

Erosion

• Streams cut their own valleys which deepen and widen over time, carrying away sediment

• 3 ways a river erodes
  - abrasion
  - hydraulic action
  - solution

Transportation

• Sediments are transported by a
  stream in the form of a rivers load.

• 3 types of sediment load:
  - Bed load: heavy sand, gravel and/or boulders

• Large sediments move via
  traction or saltation

-  Suspended load: lighter sand, silt, and clay
- Dissolved load: ions in solution from minerals that dissolved into water

Depositions

• Sediments are temporarily deposited along the streams course as:
  - Sand or Gravel Bars
  - Floodplains
  - Natural Levees
  - Deltas
  - Alluvial Fans

Sand and Gravel Bars

1. Bars in braided streams
   - deposited in highly connected small, shallow channels which water flows

2. Bars in Meandering Streams
   Where will deposition take place along a meander (bend)?
   - deposition takes place along the inside of the meander bend creating a point bar
   - erosion takes place along the outside of the meander bend, removing material and forming a cut bank

What happens to a meandering stream over time?

• Over time, meanders become more serpentine (curvy), meaning that water now must take longer to travel around a meander
  - water prefers to take the path of least resistance, so over time, the river will instead bisect the meander at its weakest spot and abandon the meander

• These abandoned meanders form one of two features (dependent on whether there is water still present or not)
  - if water is present, then we refer to this abandoned meander as an oxbow lake
  - if water has been replaced by sediment and is now dry then we refer to it as a meander scar

Floodplains

• Broad strips of land that are built up by sediment during periods when a river floods

Natural Levees

• After a flood: waters recede to the channel, leaving sediment behind, over time, ridges of sediment build up forming levee

Deltas

• Form at the mouth of a river as it flows into a large body of water (typically the ocean)

Alluvial Fan

• Resemble a ‘delta’, but alluvial fans are found within desert mountain regions
  - form ephemeral (temporary) streams after a rain event, depositing sediment in the form of large ‘fans’

Mississippi river

• Headwaters: Lake Itasca, Minnesota

• Mouth: New Orleans, Louisiana

“The captains’ return” depicts Meriwether Lewis and William Clark;s glorious return to St. Louis after exploring the Louisiana Territory from 1804-1806

New Orleans is a gorgeous city with a watery past, present, and future

• Any infamous event that has affected New Orleans?

• 2005: Hurricane Katrina caused widespread flooding throughout the city, costing billions and displacing hundreds of thousands.

• But why so much damage?

Danger Closer to Home

• The Santa Ana River (S.A.R.)

• Most Dangerous River West of
  the Mississippi

• Important Dates:

• 1825-Balboa peninsula is formed by a Santa Ana River Flood

• 1862-Santa Ana River floods after 30 days of rain

• 1938-Army Corps of Engineers deemed S.A.R. the largest flood hazard West of the Mississippi River after a flash flood resulted in 19 dead, 2K homeless and 68K acres of flooded land.

The Hydrologic cycle: Groundwater

The Hydrologic cycle:

• Water on the surface can take several paths:
  - Runoff through rivers
  - Infiltration as groundwater
  - Transpiration through trees/plants

What is groundwater?

• Water that is stored in pore spaces between grains of soil and sediment.
  - As well as narrow joints and fractures in bedrock.

• Largest reservoir of potable freshwater that is readily available to humans.
  - Water enters the groundwater system at the surface through recharge
  - Water leaves the groundwater system via discharge (rivers, lakes, oceans)

Finding groundwater

• Porosity: the percentage of total volume of rock or sediment that consists of pore spaces.

• Porosity is influenced by:
  - Grain size and shape
  - How packed or compressed the sediment is
  - The degree of sediment sorting
  - The amount of cemented material
  - only applies to sedimentary rocks

Permeability

• the ability of fluids to flow within rocks, based on well connected pore spaces are with in rock/sediment

Aquifer: layer of permeable rock or sediment that transmits groundwater freely

Aquiclude/Aquitard: impermeable layer of rock that hinders or prevents movement of water

2 types of aquifiers

1. Unconfined Aquifer

• an aquifer that is open to the surface, allowing groundwater to easily be recharged by surface infiltration

2. Confined Aquifersurizing the water.

• An aquifer filled that is bound (confined) by impermeable rock layers from above and below, pressurizing the water.

Anatomy of an unconfined aquifer

• Unsaturated (Vados) Zone:
  - area above the water table where rock, soil, and sediment are not saturated with water

• Saturated (Phreatic) Zone:
  - the water table, where relatively all pores and fractures are saturated with water.

• Water Table:
  - boundary between the saturated and unsaturated zones

Removing Groundwater

• Unconfined Aquifers:
  - Easiest and most common aquifer that water is drawn from

• Confined Aquifers:
  - Water is drawn from Artesian Wells
  - Artesian Wells occur in areas where water will rise to the surface due to release of pressure
  - Areas of released pressure are dictated by the Potentiometric Surface (water table for a confined aquifer)

Effects of pumping groundwater

• lowers the level of the water table, which can result in one or more negative impacts
  - cone of depression forms around over pumped well which can cause nearby wells to go dry
  - saltwater intrusion in coastal areas: over pumping of groundwater can disrupt the natural barriers along coastal areas between fresh and saltwaterm contaminating production wells
  - land subsidence: as aquifers lose water they begin to compress and shrink, causing the land surface to sink

Groundwater features

• hot springs/geysers

• natural springs

• karst topography

Hot springs and geysers

• what do we need? a source of heat
  - magma would be our source of heat
  - system of fractures within the rock to transmit water
  - large supply of groundwater

Natural springs

• Forms when the water table intersects the land surface

Karst Topography

• groundwater landscape that form the dissolution of carbonate rocks (limestone/marble) by acidic rainwater (groundwater

• Karst Features
  - caves
  - sinkholes
  - disappearing streams
  - speleothems:
  - stalacites
  - stalagmites
  - column

New Orleans

• The city itself is below sea level
  - between 10-20 feet below the level of the mississippi
  river and lake pontchartrain
  - shaped like a massive bow

• But why do you suppose parts of New Orleans are below sea level?
  - naturally subsides as the massive volume of accumulated river sediment slowly compacts under its own weight.
  - But, pumping water from deep aquifers for human use also contributed to the compaction of underground soil layers, accelerating subsidence.

G.R.A.C.E

• Gravity Recovery And Climate Experiment (G.R.A.C.E.) tracks changes in the amount of stored groundwater by observing changes in strength of gravity around the world

• Gravity is a direct function of mass, which means gravity is “normal” in an area when there is groundwater present

• This means that if remove excessive amounts of groundwater, gravity in the area will be less

Mitigating Groundwater Depletion Conservation

A. Conservation
1. Using more efficient irrigation systems

2. Growing more water efficient crops

B. Water Recycling

B. Water Recycling injection

• Purifying wastewater and reintroducing it back into the aquifer via injection
  - Currently being done in OC!
  - Prevents depletion, subsidence, and saltwater intrusion
  - Costs less than importing water from other place
  
  

Orange County Water District

• Provides approximately 75% water supply for north and central Orange
  County

How it this done?

• Groundwater Replenishment System (GWRS) purifies wastewater using
  three steps: Ultraviolet with with hydrogen peroxide

1. Advanced process of microfiltration

2. Reverse Osmosis

3. Ultraviolet with with hydrogen peroxide federal water standards

This purification process produces high-quality water that meets or
exceeds all state and federal water standardsore injecting it back into the groundwater system

• Its so pure that OCWD needs to add minerals back into the water
  before injecting it back into the groundwater system

Oceans

One or many oceans?

• 71% of Earth’s surface is represented by the oceans and seas

• technically 1 global ocean subdivided into 5 ocean basins
  
  

The Ocean Floor

• Bathymetry: The mapping of the ocean floor

Continental margins: Active vs Passive

• Continental margin = submerged outer edge of a continent, acting as the transition zone between the continental crust and the oceanic crust

• West Coast U.S. (active)
  - continental shelf
  - continental slope
  - trench

• East Coast U.S. (passive)
  - continental shelf
  - continental slope
  - continental rise

Passive Continental Margin

• not associated with a plate boundary

• Continental Shelf:
  - flooded extension of the continent
  - Avg shelf width is ~ 50 miles
  - Important environment for fishing, mining, and drilling

• Continental Slope:
  - gently sloping drop-off at the edge of the shelf
  - has an avg width of ~ 12 miles
  - destabilized sediment can generate turbidity currents

• Continental Rise:
  - depositional feature made of sediment at the
  base of the slope
  - Can have an avg width of hundreds of miles

Active Continental Margin

• located along or near a plate boundary where
  subducting plates form deep trenches

• Continental Shelf:
  - very short

• Continental Slope:
  - very steep

• Trench:
  deepest parts of the ocean/ planets
  surface, where subduction begins
  Often exceed depths of 10,000 m
  - The deepest trench on Earth is the Mariana Trench (35,840 ft). - Mount Everest is 29,032 ft.

The Mariana Trench

• so deep that no light reaches the trench

• water temperature is just above freezing

• water pressure within the trench is measured at 15.750 psi
  - the human body can only endure 50 psi suddenly or 400 psi over time
  - average human jaw can exert 250 psi

• there is life in the deepest parts of the trench

Ocean water chemistry

is all ocean water the same?

• ocean water chemistry is variable based on the following characteristics
  - salinity
  - temperature
  - density

Salinity

• salinity refers to the amount of dissolved “salt” in ocean water

• seawater salinity decreases with depth within the ocean

• this change in salinity with depth is known as a halocline
  - halocline indicates a rapid change in salinity near the ocean surface
  - more prevalent halocline along equatorial regions vs polar regions

Temperature

• varies based on the amount of solar radiation received

• thermocline: temperature variation with depth

• equatorial regions
  - high temperature at the surface
  - rapid decrease in temp with depth (prominent thermocline)

• polar regions
  - cooler surface temperatures
  - no rapid change in temperature from surface (no thermocline)

Density

• all liquids have different densities, and this determine whether an object (or another liquid) will float or sink

• density is the mass of a liquid divided by its volume

• factors affecting seawater density
  - salinity
  - temperature

• variations in density w/ depth = pycnocline

• Equatorial regions
  - low-density water at the surface
  - density increases rapidly with depth because of cold water

• Polar regions
  - high-density water at the surface
  - little change in density with depth

Ocean Circulation

what makes water move in the ocean?

2 types of circulation

• surface circulation

• deep water circulation (thermohaline circulation)

• The Coriolis Effect
  - because the planet rotates, traveling winds and ocean currents are forces to curve instead of moving in a straight line
  - this movement always deflects to the right in the northern hemisphere and to the left in the southern hemisphere

Ocean Gyres

• Global winds push the ocean's surface
  water, and the Coriolis effect
  immediately bends these moving
  currents into sweeping curved paths

• When these currents bump into
  continents, they are blocked and
  forced to turn, looping together to
  form giant circular patterns called
  gyres.
  
  

Thermohaline Circulation

• Global conveyor belt of water powered by
  changes in salinity and temperature

• Cold, dense water sinks in the N. Atlantic

• After water sinks, it will not reach the
  surface again for 500-2,00 years

• Deep ocean water travels through all
  the ocean basins before resurfacing
  in the North Pacific.
  
  

What are waves?

• Energy being transferred from the atmosphere to the ocean.
  - generated by wind blowing across the
  ocean surface.y of a Wave:

• Anatomy of a Wave:
  - Crest: highest point if a wave
  - Trough: lowest point of a wave
  - Wave Height: vertical distance from trough to crest
  - Wavelength: the distance between crests.
  - Wavebase: distance below the surface that is ½ the wavelength
  - marks the deepest extent of water motion in a wave.

How does water move in a wave?

• water does not actually move in the open ocean

• instead, water molecules trace a series of circles that extend below the water surface to the wave base
  - these are known as orbitals

• so, instead of “moving”, water molecules transfer energy from wave to wave

From deep sea to the shore

• as a wave travels from the deep to shallow water goes through a few changes
  - the wave now intersects the seafloor and begins to slow down
  - a decrease in wave speed cause the wave height to increase
  - a decrease in wave speed causes the wavelength to decrease
  - we can think of these like the bellows of an accordion

• eventually the wave can no longer support itself and will break on the shore

The Coastal Zone

• Foreshore: areas of the beach that is exposed during low tides and submerged during high tides

• Berm: a wave-deposited sediment platform, highest point on teh beach (transition zone)

• Backshore: area of the beach that is only covered in water during storms or exceptional tides

Beaches change with the season

• summer beach
  - lower, less intense waves
  - wider beach, build-up of sand
  - beach is lighter in color as weaker waves deposit sediment

• winter beach
  - stronger waves (due to large storms in open ocean)
  - narrower beach, loss of sand (sand builds up offshore)
  - beach is darker in color as lighter-colored sand/sediment is removed easily by string waves

Interactions between waves and shore

• wave refraction
  - the bending of a wave
  - waves arrive parallel to the shore
  - results:
  - wave energy is concentrated against the sides and ends of the headland
  - over time, wave erosion will straighten an irregular shoreline/coastline

Longshore drift

• current in the surf zone
  - flows parallel to the shore

• responsible for the net movement of sand/sediment along a coast
  - beach drift
  - zig-zag movement of sand down a beach

Erosional Coastlines

• a high-energy shoreline where waves and currents erode the land faster than sediment can accumulate, causing the coast to re4treat landward

• sea cave
  - formed by wave refraction along irregular coastlines, as headlands are eroded

• sea arch
  - forms from the continued erosion of a sea cave

• sea stack
  - the remnant of a headland that forms after the collapse of a sea arch

• Sea Arch found at Goat Rock Beach, south of Jenner, California

• Arch Rock, East Anacapa. Channel Islands National Park, California

• Sea Stack lining the coast along Big Sur

• Wave-cut Cliff: a steep rock wall on the coast that slowly gets carved away by crashing waves

• Wave-cut Platform: a rocky coastal bench that forms when waves undercut a cliff, causing the rock above the collapse and the cliff face to retreat

• Wave-cut cliff Dana Point, CA

• Broad Bench, Kimmeridge Bay, SW England

Depositional Coastlines

• low-energy shoreline with an abundant sediment supply, where waves and currents deposit material, building new land and advancing seaward

• Spit: a ridge of sand extending from the land into the mouth of an adjacent bay with an end that often hooks landward

• Baymouth Bar: a sand bar that completely crosses a bay

• Barrier Island: long sand ridges running parallel to the coast, separated from the mainland by a lagoon or bay

• Sand spit Klamath River Mouth Klamath, California

• Baymouth Bar, Humboldt Bay, Eureka, CA

• Galveston Barrier Island, Galveston, Texas

Uplifted Coastlines

• coastline that has been elevated by deep-seated tectonic forces
  - the land has risen faster than sea level, so parts of the old sea floor are now dry land

• Marine Terrance: a flat, step-like rocky bench along a coast, formed when wave erosion cuts a platform that is later lifted above sea level by tectonic activity

• Marine Terrance Goats Rock State Beach Jenner, Ca

• The largest terraces are on the Palos Verdes Hills, where 13 levels ride up to 1,300 feet

Drowned Coastlines

• sea level has been rising for the last 15,000 years
  - during the Pleistocene Epoch, sea level was ~426.5 ft below where it is today
  - that’s just over x5.5 McCarthy Halls in height

• Estuary: a coastal body of water where fresh river water mixes with ocean saltwater, formed when rising seas flood a river valley

• Fjord: a deep, narrow sea inlet with steep cliffs, formed when melting glaciers flood U-shaped mountains valleys

• Estuary, Newport Back Bay, Newport Beach, CA

• Fjord, Resurrection Bay, Seward, Alaska

Stabilizing the shore by building a beach?

• a response to coastal erosional problems
  - hard stabilization = building structures to slow sand movement

• Types of structures
  - Groin: a long, narrow wall or structure built perpendicular to a shoreline, extending from the beach out into the water, to prevent beach erosion by trapping sand. (ex: Newport Beach, CA)
  - Jetty: a long, man-made rock, concrete, or steel structure that extends from the shore out into the water perpendicular to the coastline. (ex: Newport Beach, CA)
  - Breakwater: a permanent structure built along the coast or offshore to block and absorb wave energy, protecting harbors, beaches, and shorelines from erosion (ex: Dana Point, CA)

The atmosphere

What is the Atmosphere?

• layers of gases/air that envelope the Earth

• These “gases” are divided into two categories:

  1. Permanent Gases (gases whose concentrations remain relatively stable):

     • Nitrogen (N) – 78%

     • Oxygen (O₂) – 21%

     • Argon, Neon, Helium, Krypton, Hydrogen - <1%

  2. Variable Gases (gases whose concentrations can change due to natural
     or human influence):

     • Water vapor 0 to 4%

     • Carbon Dioxide 0.035%

     • Methane 0.0002%

     • Ozone 0.000004

What is going on?

• What happened to the hot air balloon?

• Why did it happen?

  • atmospheric pressure (air pressure) caused the balloon to burst as it ascended higher up in elevation.

Air Pressure

• What is Air Pressure?

  • Air Pressure is the weight that a vertical column of ‘air’ exerts on a square inch of space

  • Average sea level pressure

    • About 14.7 pounds per square inch

• Why does air pressure change with altitude?

  • Less amount of air above you to exert pressure at higher altitudes/elevations

Structure of the Atmosphere

• Troposphere

• Stratosphere

• Mesosphere

• Thermosphere
  
  

TROPOSPHERE

• Where most weather takes place!

• Temperature ↓ as you ↑ in elevation

• Densest layer

  • 75% of atmosphere’s total mass

• Thickness:

  • Thickness varies 0-18km

  • Why does it vary?

    • Warm air expands along equator, while cold air condenses in polar regions

STRATOSPHERE

• Has steady wind but no weather

• Thickness: ~12 km to 50 km

• Temperature ↑ as you ↑ in elevation

• Contains the Ozone layer

  • O₃ gas absorbing radiation and creating heat

    • Which type of radiation does the Ozone Layerabsorb? (hint: it’s why we wear sunscreen)

What is Ozone?

• Ozone (O₃) is an odorless, colorless gas composed of 3 Oxygen atoms

• Two types of Ozone in Earth’s Atmosphere:

  • Stratospheric Ozone:

    • Found in the upper atmosphere (stratosphere) where it absorbs most of the sun’s harmful Ultraviolet (UV) radiation.

  • Tropospheric Ozone:

    • Found closer to ground-level (troposphere) in the air that we breath.

    • AKA smog, poses serious risks to human health

How does Stratospheric Ozone form?

• stable O2 in the troposphere + UV radiation will break O2 into single O in the stratosphere

• Break stable O2 into unstable single O in the stratosphere

• O2 will combine with O to for O3 (the 3 Omigos) which is more stable in the stratosphere

Why is Tropospheric Ozone bad to Breath?

• Effects on the Airways:
  - Ozone is a powerful oxidant that can irritate the air ways causing coughing, a burning sensation, wheezing and shortness of breath and it can aggravate asthma and other lung diseases.

• BAD OZONE DAYS HAVE DRASTICALLY DECREASED OVER LAST 20 YEARS!!!

  • Due to strict air quality laws set by the state of California and the EPA

What happened to the Ozone?

• Chlorofluorocarbons (CFCs)

• Manufactured under the name Freon (trademarked by Dupont)

• Used as in aerosol-spray propellants, refrigerants, solvents. And foam-blowing agents.

  • Why so versatile?

    • Nontoxic, nonflammable, and easily converts from liquid to gas in case of spillage.

MESOSPHERE

• Thickness: ~50-80 km

• Temperature ↓ as you ↑ in elevation

  • Coldest layer in the atmosphere

    (-90ºC)

• Layer where Meteors burn

• Contains ice crystals & noctilucent “night shining” clouds

THERMOSPHERE

• Home to Auroras

• Temperature ↑ as you ↑ in elevation

  • Small amount of gas moving at high speeds = high temperature

• Thickness: ~80-150km

  • Doesn’t have well-defined upper limit

• Short wavelength radiation (gamma and x-ray) absorbed by gases here!

• Satellites and Space Shuttles orbit here.
  
  

Heat Transfer

Methods

Heat is a form of energy that can be transferred or moved in three (3) different ways:

Convection

Conduction

Radiation: transfer of heat as electromagnetic waves

Electromagnetic Radiation:

• emitted by all stars (including the sun)

• Incoming Solar Radiation (Insolation) embodies radio waves, visible light, UV, and Infrared radiation

Composition of Sunlight:

• Visible Light (ROYGBV) ~ 44%

• Infrared Radiation ~ 48%

• UV Radiation ~ 7%

Light in the Atmosphere

As light enters the atmosphere it will travel and interact by traveling in three different methods:

• scattering

• reflection

• absorption

1. scattering: the light is dispersed in different directions (due to interaction with dust particles and gas molecules
   - why is the sky blue?
   - scattering of blue light that interacts with dust particles ans gas molecules in the atmosphere

Scattering also explains our reddish-orange sunsets

• light travels a greater distances at lower angles and as a result shorter wavelength light (blue light) is scattered out, leaving longer wavelength light (red and orange).

2. Reflection: light bounces back from an object at the same angle with the same intensity

Why do some surfaces reflect more light than others?

• Albedo

• overall % of Insolation reflectedby a surface.

• entire planet ~ 30% albedo

• Dark surfaces (reflect less light)

  • low albedo

• Light surfaces (reflect more light)

  • high albedo

• Fresh Snow = 80%

• Clouds = 10% - 75%

• Land Surface = 5% - 40%

3. Absorption

• 50% of incoming Insolation is absorbed by Earth’s surface

• shorter wavelengths (visible light) absorbed by surface and atmosphere

• longer wavelengths (infrared radiation) re-emitted by surface
  
  

Greenhouse gases

• Any gas that absorbs radiant energy.

  • H₂O vapor, CO₂, methane, nitrous oxide, ozone...

    • water vapor is the most abundant

    • methane is the most powerful

    • CO₂ is increasing most rapidly

      Earth’s Atmosphere:

• 78% - Nitrogen

• 21% - Oxygen

• <1% - Trace Gases

  • excludes water vapor & aerosols

Greenhouse effect

• GHGs trap some infrared energy and some escaped back into space

• insolation absorbed by land, oceans and atmosphere

• insolation it re-emitted as heat (infrared radiation)

Weather

weather vs. climate: whats the difference?

• weather is your day-to-day atmospheric mood (what you wear today)

• climate is the long-term statisticl pattern of weather average over 30 or more years (what gear you keep in your closet year-round

Weather is driven by constant energy
exchanges in our atmosphere.

• To understand how everyday conditions and severe storms develop, we look at three interconnected concepts:
  - evaporation vs condensation
  - air pressure and winds
  - air masses and fronts

Processes that change water’s state

• Evaporation
  - Liquid to Gas
  - Energy (heat) is absorbed

• Condensation
  - Water vapor (gas) to Liquid
  - Energy (heat) is released

• Why is the can wet?
  - The soda can is cooler than the air outside
  - the surface of the can is cooler
  - Warm air outside hits cool air = gas > liquid

Humidity

• The amount of water in the air is temperature-dependent
  - Warm air can hold MORE water

Measuring Humidity

• Relative Humidity (RH)
  - Amount of water vapor in the air relative to how much
  water vapor the air (at that temperature can hold)
  - Measured in % (percentage)

What Happens When The Air Has 100% Relative Humidity?

• Air is fully saturated with water.
  - means that it is holding the maximum amount of water.

• The temperature at which air becomes fully saturated is also known as its Dew Point Temperature.

If the temperature of the air is 80 °F, what would need to happen to the
temperature in order for the air to become saturated??

• Lower Temperature
  - Why?
  - As the temperature decreases, the air's capacity to hold water
  decreases as well (colder air can hold less water)
  - So… air will be getting closer to saturation/dew point

If the air is 100% relative humidity, would you feel warmer or cooler?

• warmer
  - Sweat will not evaporate into saturated air

• So if it is 75°F with 100% relative humidity, it will feel more like it is
  80°F