ENVS130 Final

geology

The study of the Earth, including earth materials, earth history and earth processes

Why is geology important?

Natural resources and economic impact, climate change, and natural hazards can affect a great number of people

scientific method, and how does it work?

1. Develop a hypothesis 2. Design an Experimental Procedure 3. Draw onclusions and think beyond--revise, learn more The scientific method is not a checklist but rather a web. Steps may be repeated, or you may go back and forth between steps as you get new information and communicate with others. It's an unpredictable, dynamic process.

hypothesis

A proposed explanation for a phenomenon hat can be tested--should be in the form of a prediction, not a question

1 km to m

1000

1 m to cm

100

1 cm to mm

10

1 mi to ft

5,280

1 ft to in

12

An inch is divided into how many sections?

16

1 kg to g

1000

1 L to mL

1000

1 milliliter is the same as

_______ 1 cubic centimeter

ratio

A simple expression comparing two quantities

density of water

1 g/cm^3 (or 1 g/mL)

What are the two kinds of crust, and what makes them different?

Continental crust is very thick (avg. 35 km) and less dense (2.8 g/cm^3) composed largely of granitic rock | Oceanic crust is much thinner (avg. 8 km) and more dense (3.1 g/cm^3)--composed mainly of volcanic basalt

What are the layers of the earth?

Inner core: nickel and iron, solid despite heat because the pressure is so high; Outer core: liquid nickel and iron, causes earth's magnetic field as it flows around core; Mantle: semi-molten rock, semi-solid and can flow, onvection here drive plate tectonics; Crust: thin rocky outer layer we interact with

What is thought to cause magnetic reversals, and what is the magnetic field like around the time of a reversal?

Magnetic reversals are thought to be caused by disorganization and reordering of movement in the liquid core. The magnetic field becomes tangled, weakened, and disorganized until it finally reverses, which takes an average of 7000 years. During this time, technology may be affected, and earth may be less shielded from harmful radiation.

How can rocks serve as a record for magnetic reversals? How does this relate to sea-floor spreading?

When molten rock containing iron cools, the iron minerals line up with the magnetic field at the time, recording the alignment of the magnetic field at the time the rock formed. Since rock is always being created at mid-ocean ridges through sea-floor spreading, sea-floors can act as a continuous record of Earth's magnetism going back 180 million years.

What drives convection in the mantle?

Changes in heat, volume, and density of the semi-molten rock as it is heated by the core

What occurs at plate boundaries?

Earthquakes, volcanoes, creation of new crust, destruction of crust

What are the three types of plate boundaries, and what features are associated with them?

Divergent--spreading apart ea-floor spreading, new crust, rifting--sometimes volcanoes, earthquakes, or hydrothermal features like hot springs | Convergent--moving together Subduction zones (continental-oceanic collisions), flux melting, destruction of crust, volcanoes, earthquakes, mountain-building (continental-continental collisions) | Transform--moving side-to-side Earthquakes, fracture zones (when you have a combination of divergent and transform)

subduction zones

Occur when an oceanic plate is sliding (being subducted) beneath a continental plate. Molten rock rises up and forms a line of volcanic mountains.

flux melting

Occurs when subduction drags water with it beneath the crust, causing it to melt faster. This creates many more volcanoes.

How do hot spots form?

Hot mantle material rises up in a mantle plume, which stays put while plates move above it. This can form a chain of volcanic islands.

mineral

A naturally-occurring substance found in the earth with all three of the following characteristics: 1. ordered atomic structure 2. specific physical properties 3. characteristic chemical composition !!NOT the same as rock!!! Rocks are made up of minerals

ionic bonding

Transfer of electrons from one atom to another; creates a positive and negative ion and may result in solubility

covalent bonding

Sharing of electrons between two atoms; creates very strong bond

metallic bonding

Pooling of electrons in a cloud between metal atoms; creates conductivity and metallic luster

Van der Waals bonding

Weak temporary bond due to attraction between dipoles of atoms

characteristics of minerals

Crystal shape, Color, Luster, Hardness, Streak, Specific gravity, Cleavage, Fracture, Effervescence, Fluorescence, Phosphorescence

polymorphs

Minerals with the same chemical composition but different properties (ex. diamond and graphite--polymorphs of carbon)

two most common minerals on Earth

Quartz and feldspar

mineraloids

Substances similar to minerals but not technically minerals

rock

A naturally-occurring group of one or more kinds of minerals

igneous rocks

Rocks that cool down from melted rock (lava or magma)

two categories of igneous rock and how do they differ?

Extrusive: cools quickly on the surface of the earth after being exposed to air or water during an eruptio, fine-grained | Intrusive: forms by cooling slowly underground, large crystal size, since minerals have a chance to grow into large crystals, coarse grained

What are the three kinds of volcanoes?

Composite: made of layers of hardened ash, lava, and pumice | Cinder cone: made of layers of extrusive igneous rock called scoria | Shield: flatter volcano made of hardened lava flows

dike

A vertical intrusive igneous rock formation that cuts across rock layers

sill

A horizontal intrusive igneous rock formation that forms between rock layers

batholith

A huge pocket of magma cooling slowly underground; large mineral crystals often form here

aphanitic texture

A fine-grained texture of extrusive igneous rocks; indicates rapid cooling

phaneritic texture

A coarse-grained texture of intrusive igneous rocks; indicates slower cooling

porphyritic texture

Large crystals in fine-grained rock; large crystals are forming in magma chamber, and then change in pressure causes them to erupt so the rest cools quickly; intrusive AND extrusive

pegmatitic texture

Exceptionally large crystals fastened together; indicates very slow cooling, as in a batholith; intrusive

vesicular texture

Appearance with holes and bubbles; caused by gas escaping lava

glassy texture

Forms from volcanic material cooling down instantly into chunk of glass; extrusive

pyroclastic texture

Formed from ash and rock fragments that settle to the ground and compress into rock; extrusive

What are the four color categories of igneous rocks? From darkest (least silica) to lightest (most silica)

Ultramafic, Mafic, ntermediate, Felsic (feldspar + silica)

xenocrysts

Foreign minerals stuck in an igneous rock

How do sedimentary rocks form?

By combining pieces of broken rock or biological materials, through chemical processes, from the erosion of igneous and metamorphic rocks

Clasts

the pieces of sediment that make up sedimentary rocks (ex. silt, gravel, clay, sand)

What are the four main processes involved in forming sedimentary rocks?

weathering/erosion; transport; deposition; lithification

trace fossils, and what do they tell you?

Trackways, burrows, footprints left behind by living things; tell you what animals lived in the area

How do metamorphic rocks form?

When igneous or sedimentary rocks are changed from one form to another by extreme heat, pressure, or both

What are parent and daughter rocks?

The original igneous or sedimentary rock is called the parent rock, and the metamorphic rock it turns into is called the daughter rock; daughter rock often looks and acts differently from parent rock

foliation

Alignment of minerals in planes perpendicular to stress; associated with direct pressure

metamorphic grade

Amount of heat and pressure the rock is under; low grade is under lower heat and pressure, high grade is under higher heat and pressure

What are the four kinds of foliation from low to high metamorphic grade

Slaty cleavage: flat foliation, rock breaks into sheets | Phyllite texture: wavy and wrinkled foliation; minerals are getting more coarse and reflecting light better as they line up; satiny or metallic luster | Schistosity: very foliated, even more coarse, shiny, and layered, glittery, shiny layers of platy minerals like mica | Gneissic banding: so foliated that minerals completely separate into light and dark strips--highest temperature and pressure

What are the non-foliated textures of metamorphic rock?

Crystalline--coarse-grained crystals of mostly the same size | Microcrystalline--fine-grained microscopic crystals

ore

A rock deposit that contains concentrated mounts of economically useful minerals

What concentration of a mineral deposit would make it economically viable for mining?

100-1000 times the concentration of ordinary rock

Ocean floor mining

extracting minerals from water or rocks on the seafloor, difficult and expensive, not usually worthwhile yet due to lack of technology

Mechanized surface mining

exposing minerals by blasting away the surface and extracting using machinery

Mountaintop removal surface mining

removing the top of a mountain in the process of surface mining to get at minerals within (often coal)

Surface mining and quarrying by hand

associated with many social justice problems around the world, difficult working conditions, may be worked by slaves or indentured servants

Subsurface mining

underground coal and mineral mining, tunnels beneath the surface

Solution mining

removal of minerals by dissolving them in hot water or acids injected underground

conflict mineral

A mineral mined in a territory that is experiencing war and being sold to fund the war effort (Coltan in Democratic Republic of the Congo, "blood diamonds" in many places in Africa with unstable governments)

What is the relationship between earthquake magnitude and frequency?

Lower magnitude earthquakes happen frequently, but frequency decreases with magnitude, so higher magnitude earthquakes happen less often

Moment-Magnitude scale

used instead of the Richter scale to measure earthquakes, calculated using length and depth of the fault, amount of displacement on the fault surface, and strength of the rock that was faulted, quantitative logarithmic scale from 1 to 10

Mercalli Intensity scale

qualitative scale used to measure earthquakes along with the moment magnitude scale, based on observations and descriptions of what happens, scale of 1 to 12 in Roman numerals, varies depending on the place and is used by authorities to understand how the earthquake affected people in a certain area

Richter Scale

logarithmic scale from 1 to 10 used to measure earthquakes; no longer used by scientists

Body waves

go through the rock layers of the Earth; there are two types of body waves: P-waves and S-Waves; P-waves (primary waves) are the fastest type of wave and are compressional waves; S-waves (secondary waves) are slower than P-waves but still very fast, and travel in S-waves with an up and down motion

Displacement

movement along a fault, when rock layers shift in response to an earthquake

seismic waves & the types

waves of energy caused by an earthquake; two main types of seismic waves: body waves and surface waves

epicenter

point on the surface directly above the focus, where the most damage is felt

Earthquake

a sudden release of energy because of stresses and strains in the Earth's crust

focus

place in the crust where the rupture and the earthquake actually occur (NOT the epicenter)

What are the five characteristics of dinosaurs?

1. Lived during the Mesozoic Era; 2. An upright posture in which legs come straight down from body (not sprawling posture); 3. Bird-like or lizard-like hip anatomy; 4. Two openings in the skull behind the eyes; 5. Lived and moved on land (not in the air or sea)

pterosaurs

First flying vertebrate reptiles, not dinosaurs; structure of wings was different from other flying animals--essentially arms with very long 4th digit and webbing attaching it to the body; Different from bird and bat wings

What caused the Permian Mass Extinction?

Associated with major period of global warming; Huge volcanoes were opening in Siberia, spewing greenhouse gases that caused the planet to warm up; This caused oceans to release methane hydrates, which caused more warming; Ocean circulation was affected; noxia (lack of oxygen) in oceans; Vicious cycle, ultimately led to 95% of species going extinct

What caused the Triassic Extinction?

Mass extinction on land and sea; Killed 50% of marine fauna; Caused by volcanism and Pangaea rifting: habitats torn apart, difficult environment

Syncline

type of fold with down-folded rock layers (looks like a u); youngest rocks in the center

Other types of folds

Asymmetrical fold: folds that aren't all symmetrical, which occur when there is more stress in one direction than in another; overturned fold: fold turned on its side; dome: circular anticline with oldest layers in center; basin: circular syncline youngest layers in the center

Features of faults

scarp: exposed cliffs of rock | footwall: block that moves on the under surface of the fault (looks like a foot) | hanging wall: block that moves on the upper surface of the fault

Normal fault

form from tensional stress and divergent boundaries; crust is pulling apart and lengthening; hanging wall moves down relative to footwall

Reverse fault

form from compressional stress and directed pressure; crust is pushed together and shortened (convergent boundaries); hanging wall moves up relative to foot wall

Strike-slip fault

crust is neither lengthened nor shortened; crust moves sideways relative to another piece of crust; occurs at transform boundaries and causes earthquakes; can be left-lateral or right-lateral

Joints

fractures in rock formations caused by brittle fracture of rocks from stress

Anticline

type of fold with arched rock layers; oldest rocks in center and limbs dip away from center; mnemonic: "A" is for Arch and Anticline (an anticline looks like an arch)

Folding

type of ductile deformation; previously flat layers become folded and tilted; can be small or very large (a whole mountain, for example); contain limbs, fold axis, and axial plane

What is the relationship between frequency and magnitude?

Frequency and magnitude are inversely related (As magnitude rises, frequency decreases); Small events happen often, large events are rare

Natural hazard

Any natural occurrence that has the potential to cause damage or loss of life

What caused the Cretaceous Mass Extinction, and what were its effects?

Asteroid was the primary driver, although volcanoes played a role; Killed all dinosaurs (except birds), Killed ammonoids, Killed Mosasaurs and other marine reptiles, Killed 90% of calcareous plankton, Many dominant species were gone, so there was an opportunity for mammals to take their place

"living fossil"

An organism that has very ancient ancestors and hasn't changed much through time; these organisms can provide a window into the past

What caused the Ordovician Extinction?

Associated with a big ice age; earth was getting cooler, glaciers were forming; as glaciers formed, water was trapped on land, and ocean level dropped; Loss of shallow water habitats; All life at this point was in oceans, so loss of shallow water caused mass extinction

When are the first fossils from, and what were these fossils called?

3.5 billion years ago in the Precambrian | Stromatolites: layered structures of cyanobacteria, These are important because they were the first photosynthesizers and were responsible over billions of years for changing our atmosphere and providing the first oxygen to make the atmosphere breathable

unaltered soft parts

Soft structures of organisms are preserved (very rare but important), Structures may be dried out, preserved in amber, frozen, etc.

unaltered hard parts

Hard structures like shells and bones are preserved exactly as they were when alive; Example: Nacre ("mother-of-pearl")