Earth Science Midterm I

All info on the study doc provided by Monica + things she has mentioned in class that are going to be on the exam

Geology

Based on the law of uniformity and the law of superposition

Law of uniformity

Anything that happened in the past happens today in terms of geological activity

Law of superposition

Older rock below, younger rock on top aka layer on bottom deposited first so must be older

Radiometric dating

Aka absolute dating → uses radioactive isotopes. Parent element decays a daughter element

Half life

The time required for ½ of a parent material to break down to daughter material

What do you use for radiometric dating?

Carbon 14 for younger (less than 25,000 yrs) aka to date biological remains → carbon is incoporated into the cells of living organisms and begins to decay when the organism dies: half life of 5,700 yrs

Uranium 238 for rocks → larger half life (4.5 billion yrs)

Relative dating

Less precise and gives the relative age either older or younger

Law of superposition, use of index fossils, correlation of rock layers

Used when absolute age is not possible

Extinctions

• 99.9% of species that ever lived are extinct

  • Usually die off after 2-10 million years

• Mass extinctions (50-70% of species die off) mark the boundaries between eras

• In 6th mass extinction rn, losing species at a rate 1000x previous extinctions 

Fossils, imprints, or casts of living organisms are usually on what kind of rocks?

Sedimentary rocks (rock that has been modified by water so the rock is softer)

Fossil index

Can determine the relative age of sediments

Earth Science

The study of the earth and its components, and the basis for environmental science

Branches of Earth Science

Geosphere, atmosphere, hydrosphere, and the biosphere which is conditioned by the other three

Scientific Method

Formulate hypothesis, then you collect data and make observations and if you can prove your hypothesis you can accept the theory → is pretty modern way of thinking (started in the Enlightenmnet)

Big Bang Theory

Relativity Theory and Doppler Effect

Universe was formed 15 bya from a singularity exploding, momentum and energy → everything started to spin → material that was similar started to go through accretion (stars, planets, solar systems, galaxies)

Doppler Effect

The separation of planets and stars → first observed by Edwin Hubble

How many habitable planets are there in the Milky Way?

40-100 billion habitable planets

Density stratification

The vertical layering of fluids (like water or air) into distinct horizontal zones based on differences in density

Accretion

The formation of a terrestrial planet (4.5 bya)

Definition: The gradual increase in size or growth of an object or landmass through the external addition, accumulation, or buildup of new layers and materials over time

When was the Earth formed?

4.5 bya (layered earth) → dated the oldest rock to be that age (oldest rock found in Australia)

Differences between inner and outer planets

Telluric planets vs. cold giants

Telluric planets

Atmosphere, material is similar, evidence that there was liquid water at some time… → telluric planets are missing oxygen so no Ozone layer, liquid water, or life

Formation of Earth by density stratification

Core, mantle, and crust

Primitive Earth

Very unstable, atmosphere was full of CO2/ammonia/methane and had no oxygen (PRIMORDIAL ATMOSPHERE), no water, other toxic gases, electrical storms, no protection from the sun, a lot of earthquakes and volcanic activites

Sources of Earth’s water

Came from outgassing of mantle material (water vapor pockets) OR ice comets bombarding Earth for millions of years

Source: 3.7 bya, oldest sedimentary rock

Secondary Atmosphere

When water appeared, the temperature started to stabilize leading to the Secondary Atmosphere

Primordial soup theory

Most accepted theory for the origin of life.

• Between 1 and 2 bya, life formed in the bottom of the ocean floor, near the hydrothermal vents

  • Life has to: metabolize, grow, and reproduce

  • Water is an ideal medium for life because it moderates temperature, retains heat, and dissolves nutrients 

• Autotroph -> makes their own energy (from sun or chemical gradients)

• LUCA -> last universal common ancestor (ON TEST)

  • Started in hydrothermal vents 

  • Likely from white smokers -> probably hydrothermal vents in lost city

    • Rich in methane and alkaline 

• ⁃ Gave it components to support first organisms of earth

Panspermia hypothesis

Hypothesis that life or its organic building blocks exist throughout the universe and were distributed to Earth by comets, meteoroids, or asteroids
Astrobiology, fossil of a bacteria on a meteorite form mars

Definition of life

Grow, reproduce, metabolize

Creation of the ozone layer

Oceans became full of oxygen and then the atmosphere was created!

Evolution of Earth’s Atmosphere aka What Happened

There has been three atmospheres

1st Step: Primitive/primordial atmosphere: how earth was formed, that was no water, and what in the atmosphere.

• No O2, a lot of CO2. Electric storms.

2nd Step: Appearance of water led to secondary atmosphere.

• Where did water come from

• What are the characteristics of water to make ideal for life:

  • Retains heat

  • Moderates temp

  • Transports and dissolves nutrients

  • In this primordial soup life appeared: grow, reproduce and metabolize.

  • What did this little bacteria do? Intake CO2 and produce o2,

  • Archaea appeared 1bya.

3rd Step: Modern atmosphere: once the ocean were full of O2, the atmosphere became full of oxygen and the ozone layer formed (modification of earlier atmosphere via life processes → removal of carbon dioxide, enrichment of free O2)

Once everything became stable the Cambrian Explosion 500 mya

Characteristic of water for life

Retains heat, moderates temperature, transports and dissolves nutrients

Formation of Atmosphere

Modern atmosphere when the ocean was full of O2 → atmosphere full of oxygen leading to the ozone layer

Cambrian Explosion

Biology’s big bang, ~540 mya

Transitioned Earth from simple single-celled or small colonial organisms to complex, multi-celled organisms (first plants = algae, first animals = jellyfish and trilobites)

Plate tectonics

Pieces of lithosphere that move independently from each other on top of the mantle atmosphere 

• Lithosphere = crust + mantle 

• On top of asthenosphere (weaker part of mantle in a plastic state) 

• Based on sea floor spreading and continental drift

First Crust

Basalt → dense, heavy → becomes granite which is lighter

Basalt is the ocean floor, granite is the continents

Theory of Plate Tectonics

• Alfred Wegner set up the theory of continental drift based on five lines of evidence

  • Jigsaw fit (coastlines fit tgt), geological fit (geology aka rocks continuous across continents), tectonic fit (old mountain belt across multiple continents), glacial deposits (suggest ice flowed from central point), fossil evidence (same fossils across continents)

  • No plausible mechanism to explain how and why plates move

• Wegner used geological, biological and meteorological evidence

  • Pangea and then continents drifted apart

  • 1930s: convection cells in mantle proposed by Arthur Holmes

  • Hypothesis was rejected becaue he couldn’t prove how continents split

• 1950s: worldwide effort to map the ocean floor, data collected

Wilson’s contributions to plate tectonics

1. Formation of volcanic islands in middle of the oceanic plates (hotspots on the mantle leading to volcanic island chains like Hawaii)

2. A new type of plate boundary, the transform fault (missing piece of plate tectonics)

3. Unified theory of plate tectonics (explained plate tectonics, also know as the Wilson cycle: oceans open, the ocean is consumed along a trench by subduction and closes, producing
   continental collision)

Bathymetry

The scientific measurement and study of the underwater depths of ocean floors, lake beds, and river channels (underwater equivalent of topography, illustrates 3D features of ocean floors)

Ridges and trenches

Temperature

Hot temperature at ridges

Sediment age

Ridge younger sediment and the trenches older

Seismic activity

Earthquakes at trenches and volcanic activity at ridges

Tectonic Plates

Pieces of the LITHOSPHERE (crust+mantle) that move independently from each other on top of the MANTLE ASTHENOSPHERE (weaker part of mantle in a plastic state)

How plate tectonics works

The crust is divided into plates that diverge (CREATING RIDGES), converge, creating trenches in the oceans, or slide past each other #faultlines

How many plates are there?

Seven major plates: Pacific, North American, Eurasian, African, Antartica, Indo-Australia, South American
21 small plates

Diverging boundaries

Move away from each other aka plates separate and go in opposite directions

• Allows for new lithosphere to form from upwelling magma

• Occurs at mid-oceanic ridges (called seafloor spreading) or rifted continental margins

  • continental rift valleys (ex. East Africa rift valley): where continental plates are broken

  • mid-ocean ridges: where oceanic crust is created as new crust forms along the ridge when old crust splits and magma rises to fill the gap

• Crust production

Ex. Iceland, Red Sea

Convergent boundaries (general)

Plates move toward each other

• One plate sinks beneath the other along a subduction zone or the plates collide becasue neither can be subducted

Converging Ocean to Ocean

Trenches, oceanic volcanic arcs

Mariana’s trench

Converging Ocean to Land

Continental volcanic arcs

Peru-chile, longest trench (9000 km)

Ex. the west side of South America where the Andes are

Converging Land to Land

Mountain belts

Ex. Himalayas Mountains (Indo-Australian CRASHED into Eurasian plate)

Transform Plates

Locations where two tectonic plates slide horizontally past one another aka convervative boundaries

San Andres Fault

Discovered in 1965 by Wilson → missing piece in the puzzle of plate tectonics

Ring of Fire

Area in the Pacific surrounding the ocean basin where there is high seismic activity aka sea-floor spreading

What is happening to the Atlantic and Pacific basins?

Atlantic Basin - EXPANDING, Pacific Basin - SHRINKING

Types of crust

Oceanic aka basalt

Continental aka granite

Oceanic Basin division

Divided into continental margins and the sea floor

Continental Margin

Submerged edges of continents, account for 15% of Earth’s crust

Passive or Atlantic (inactive suture btwn continental and oceanic lithosphere) - if land/continent is touching just ocean/floating

• permit long beaches to form

Active or Pacific (from subduction or sliding aka convergent and transform boundaries) - if land/continent is touching edge of plate

• creates cliff coasts, sites of earthquakes

Parts of ocean basin

Continental shelf (active vs. passive), continental slope (deep edge of oceanic crust), abyssal plain (flat, deep sediment on ocean floor btwn ridges and inactive margins of continents), volcanic arc, volcanic island, coral reef, trench, continental rise (in passive margins, sediments from turbidity currents), seamounts (steep inactive volcanos), guyots (flat-topped seamounts)

Submarine Canyons

Where turbidity currents are tested for energy

Abyssal Plains

Largest plains on earth, wate ris unique, oldest and never mixed

Oceanic ridges

Second largest feature (25% of crust) formed by diverging plates

Have hydrothermal vents

Trenches info

Peru-Chile trench, deepest point is Challenger deep

Volcanic islands

Ex. Chain islands - Hawaii Islands, Canary Islands, Galapago Islands

Fixed hot spots in the mantle

Atoll formation order

An atoll is an island of coral that encircles a lagoon partially or completely

1. Volcanic island

2. Seamounts

3. Guyots

4. Atolls

Island Arcs form parallel to trenches

Ex. New Zealand, Caribbean Islands, Aleutian

Atoll

Form on top of guyots and are formed by coral reefs

Atolls are sinking (FALSE) but sea level is rising (TRUE)

Changes in the coast

Eustatic sea change → worldwide changes in geological time frame due to plate movement, climate variability, local sea level, weather conditions

Common over the past 1my

VS.

Local sea level change → uplifting coastlines (tectonics, earthquakes), subsiding coastlines (karstic areas/limestone), currents, seiches, and storm surges

Primary Coasts

Coasts dominated by terrestrial processes

• Erosion - drowner river or glacier valleys, fjords, Chesapeake Bay, Rias in Galicia

• Depositional - sediments that come from rivers and form deltas, Ebro River, Mississippi, Amazon, Nile

  • Threats are dams and climate change

• Volcanic - Hawaii, island

• Fault - Earthquakes, California

Erosion Coasts

Primary coast terrestrial process

Coasts w/ erosional features that formed during low sea level and are now flooded

• ex. flooded coastal river valleys (Chesapeake Bay), flooded coastal glacial valleys (fjords)

Depositional Coasts

Primary coast terrestrial process

Coasts that deposit more material than removed by marine processes

• ex. river deltas (ganges delta), glacial moraines

  • Deltas are formed by sediments deposited by rivers on the coastline

Volcanic Coasts

Primary coast terrestrial process

Coasts formed by lava flows

Fault Coasts

Primary coast terrestrial process

Vertical fault movement along a coast can cause land to uplift or subside VS. horizontal fault movement can cause the opening of a gulf or a linear shoreline

Secondary coasts

Coasts dominated by marine processes (ex. waves action in conjunction w/ terrestrial erosion)

• Chemical weathering

• Physical erosion

Features: sea stack, sea caves, sea arches, beaches

Factors:

• different rock types are chemically weathered (dissolved at different rates)

• different rock types are physically weathered (abraded) at different rates

• wave energy

  • high energy coasts have more frequent large waves (ex. maine, tip of South America and tip of Africa)

  • low energy coasts are in protected areas (gulf of mexico)

Depositional Coasts

Secondary coasts

• erosion, transport, and deposition of sand by waves

shore straightening, longshore drift

Biologically modified coasts

Secondary coasts - organisms responsible

• saltmarsh plants in temperate regions

• mangroves and coral reefs in tropical and subtropical regions

Wave refractio

Waves coming in at an angle

Riptide

Waves parallel to shore

Longshore current

Produced by wave refraction, transports sediments, produces beaches

Beaches

Winter beach: steep slope and a lot of erosion

Summer beach: gentle slope and a lot of deposition

Natural storage of sand

dunes and the sand is held with dune vegetation that have long roots

Features the longshore current produces

• San spit

• Bay mouth bar

• Inlets

• Barrier island

• Lagoon

• Longshore bar

Biologically modified coats

Coastlines modified by living orgnasims

Functions of biologically modified

Prevent erosion, storm surges, nurseries, filler water from inland, habitat, recreational activities

Three solutions to coastal erosion

retreat, accommodate, and protect (soft vs. hard protection)

Coast line eroded…

Coastal development, climate change, longshore current interruption

Isostacy movements

Form of mountain building

Balancing crust until equilibrium is reached

Principle of isostasy = parts of crust will rise or subside until these parts are buoyantly supported by their roots

• mountain ranges have thick roots of continental material that extend into mantle

• as mountains erode and mass becomes smaller, roots will become smaller

• balance between erosion and decrease in size of root will continue for hundreds of millions of years until both mountains and their roots disappear

Isostatic rebound = slow process of crust’s rising

Mountain belts

Large group of mountains including mountain ranges and mountain systems

Two (American aka Circum-Pacific, euroasian aka Eurasian-Melanesian)

• located along convergent plate boundaries

Mountain criteria

Needs to be an elevation of more than 600 meters high

Types of mountains

Folded (ex. Appalachian Mountains)

• Rock layers buckle and are squeezed from opposite sides

• highest mountain ranges in the world

• show evidence of ingenious activity and faulting

dome (Adirondacs)

• molten rock rises through curst and pushes up rock layers above it

• forms a circular dome on earth’s surface

volcanic mountain (Hawaii)

• when molten rock errupts onto surface

• develop on land or oceanic floor

• largest found on divergent plate boundaries of mid-oceanic ridge

Fault block (Tetons)

• crust is broken into large blocks and lifted above surrounding crust

• faulting tilted blocks form gently sloping moutnains

• grabens - long, narrow valleys formed when large blocks of curst have dropped between normal faults

mountain ranges, ridges, belts

Orogeny

process that forms all mountain ranges

• creates broad, linear regions of deformation known as orogenic belts

• belts are associated w plate boundaries usually