Geoscience Final Exam

Describe the formation of the Universe and elements.

- Earth formed 4.5 billion years ago due to the Big Bang

- The first element created after the big bang was hydrogen

Identify how the Earth is one of eight planets in the solar system, the inner four being rocky, and the outer four being gas-rich.

- Earth is special because it is an ocean planet. Water covers 70 percent of Earth's surface. Earth's atmosphere is made mostly of nitrogen and has plenty of oxygen for us to breathe. The atmosphere also protects us from incoming meteoroids, most of which break up before they can hit the surface.

-What is the physical state of the three groups of solar planets?

I: rocky, II: gaseous, III: icy

- The composition of the giant (jovian) planets is mainly gas and ice

Describe Earth's structural layers, including how they are arranged and what the abundance elements are.

- Earth materials are organized by density

- Crust (lithosphere and asthenosphere); mantle, outer core, inner core

- Element in center of Earth: iron

- Three major heat sources of the earth:

Sun

Radioactive decay

Planetesimal collision

Explain the importance of the magnetic field for life.

- The Earth's magnetic field serves to deflect most of the solar wind, whose charged particles would otherwise strip away the ozone layer that protects the Earth from harmful ultraviolet radiation.

- All of earth's gold is generated by:

Supernova explosion

- The oxygen on earth is generated by:

Dead star

- Our solar system began as a:

Second or third generation nebula

Confirm understanding of continental drift hypothesis, including the lines of evidence that supported it.

- Alfred Wegener: His hypothesis was that the continents had once formed a single landmass, called Pangaea, before breaking apart and drifting to their present locations.

- This was proved to be true due to plate tectonics.

Confirm understanding of sea floor spreading, including the lines of evidence that supported it.

- Seafloor spreading is the theory that oceanic crust forms along submarine mountain zones, known collectively as the mid-ocean ridge system, and spreads out laterally away from them. (proposed by Harry H. Hess in 1960)

- By the use of the sonar, Hess was able to map the ocean floor and discovered the mid-Atlantic ridge (mid-ocean ridge). He also found out that the temperature near to the mid-Atlantic ridge was warmer than the surface away from it. He believed that the high temperature was due to the magma that leaked out from the ridge. The Continental Drift Theory of Alfred Wegener in 1912 is supported by this hypothesis on the shift position of the earth's surface.

Explain the difference between lithosphere and asthenosphere.

Lithosphere: the rigid outer part of the earth, consisting of the crust and upper mantle.

Asthenosphere: the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur.

Explain the difference between crust and lithosphere, and between asthenosphere and mantle.

- The crust (whether continental or oceanic) is the thin layer of distinctive chemical composition overlying the ultramafic upper mantle, while the lithosphere is the rigid outer layer of the Earth required by plate tectonic theory.

- Asthenosphere: Relatively soft and can flow

If you poke it, it can dent, but it does not really flow

Differentiate between active and passive margins, and locate examples of each.

How does seafloor spreading push the continents around?: Passive margin

An active continental margin is found on the leading edge of the continent where it is crashing into an oceanic plate. An excellent example is the west coast of South America. Active margins are commonly the sites of tectonic activity: earthquakes, volcanoes, mountain building, and the formation of new igneous rock.

Passive continental margins are found along the remaining coastlines. Because there is no collision or subduction taking place, tectonic activity is minimal and the earth's weathering and erosional processes are winning.

Plate Boundaries

check study guide for diagram

Explain how the plates are created and consumed and how the mountains are uplifted.

When continents break apart:

- Initial uplift due to heat transfer

- Rift valley is formed, elevation lowering due to consolidated dense asthenosphere material

- New ocean basin composed of newly formed dense lithosphere

- Ocean widens

Minerals

Solid

Naturally occuring

Definable chemical composition

Uniform atomic structure

One or more elements

Rocks

Naturally occurring

Coherent

An aggregate of minerals or a body of glass

3 common rock-forming minerals.

Biotite

Na-plagioclase feldspar

Orthoclase feldspar

Quartz

Explain the primary ways in which minerals form.

Crystallization from magma

Precipitation from solution (Ex. seawater evaporates)

Metamorphism (high heat and pressure)

Top 3 Elements in Earth's Crust

oxygen, silicon, aluminum

Top 3 Elements in Entire Earth

Continental crust: lighter, less dense minerals

Oceanic crust: darker, denser minerals

Core: iron and nickel, molten in outer core

Mantle: minerals stable under high temps and pressures (Fe and Mg-rich

Different textures of rocks (sedimentary)

Clastic: crystal glued together by cement, which is composed of minerals precipitated between crystal grains

Crystalline: crystals held together by interlocking each other

Different appearances of rocks

Glasses: no visible crystal structure

Foliage: with leaf-like layers

Vesicular: with void spaces

What is the major group of rock-forming minerals in earth's crust?

Silicates

Which of the three rock types do you think is the most abundant in the crust?

Igneous (from magma)

Identify the 3 major rock types and where they can be found on (or in) Earth

Igneous

Metamorphic

Sedimentary

Volcanic (Extrusive) Rocks

Form when magma rises to earth's surface. Can be crystalline, clastic, glassy, or vesicular

Basalt (oceanic crust)

Intrusive Rocks

Form when magma solidifies below earth's surface. Always crystalline

Granite (continental crust)

Explain how the characteristics of an igneous rock (color and texture) provide information on its cooling history and silica content.

Igneous rocks with large mineral crystals were cooled slowly (ex. Underground magma chamber)

-Cooling quickly results in intrusive rocks with larger grains

-Cooling slowly results in extrusive rocks with finer grains

Basalt

mafic, extrusive, formed from the rapid cooling of magnesium-rich and iron-rich lava. Dark-colored and fine-grained

Rhyolite

felsic, extrusive rock. Pink or gray in color and fine-grained

Granite

felsic, intrusive rock, coarse-grained and pink, white, and grey in color. Composed mostly of quartz, orthoclase, and feldspar

Gabbro

mafic, intrusive, formed from slow cooling of magnesium rich and iron rich magma, coarse-grained

Peridotite

coarse-grained igneous rock, ultramafic, intrusive, dark-colored

Oceanic Crust

basalt (volcanic extrusive igneous rock)

Continental Crust

granite (intrusive igneous rock)

Determine whether or not a given igneous rock sample is intrusive/volcanic/mafic/felsic.

- Felsic (high silica content): light colored

- Intermediate: mixed colors, both light and dark

- Mafic (iron, magnesium rich, dark colored)

Partial Melting

Partial melting: Some minerals melt and some don't.

- Felsic minerals = lowest melting temps

- Mafic minerals = highest melting temps

Partial melting of (ultramafic) mantle forms mafic magma

Partial melting of continental crust forms felsic magma

What is the magma composition at the mid-ocean ridge?

mafic

Explain the processes of fractional crystallization and how that can change the composition of a magma.

When magma cools, which minerals will crystallize (solidify) first?: Mafic (Low Si)

What is the typical composition of magma forming at the continent-ocean subduction zone?

Felsic to intermediate

Three types of sedimentary rocks

Clastic (ex, sandstone, shale): Composed of centered mineral grains/rock fragments

Chemical (ex. Rock salt, gypsum): Have a crystalline texture, Initial crystal growth in solution, Recrystallization during burial

Biochemical/organic (ex. Limestone, chert, coal, oil, shale): The soft tissues of living things, Calcite shell debris, Silica shells (of diatom, etc)

Describe the four steps in the formation of a clastic sedimentary rock.

1. Breakdown of rock to form sediments

- Weathering: physical and chemical

2. Transportation of sediments

3. Deposition of sediments

4. Lithification

List (and explain) various factors that control the rate of weathering in a given area.

- Fractures - faster with more, larger fractures (physical)

- Climate - faster with freeze/thaw cycle (physical)

- Climate - faster with abundant water for chemical weathering reasons

- Vegetation - faster with roots, burrow (physical)

- Rock type - faster with rocks subject to chemical weathering (example: quartz vs, calcite)

Describe the likely depositional environment of the sediment that makes up a clastic sedimentary rock (based on its characteristics).

- Boulders, cobbles, pebbles

- Sand: coarse, medium, fine

- Clay and silt

Given a specific depositional environment, name the rock that would likely form if the sediment found there were lithified into rock.

Common clastic sedimentary rocks: Breccia, Sandstone, Shale, Conglomerate

Red rocks: formed on land, oxidizing environment

Gray rocks: under water, low oxygen conditions

Size, shape, sorting: strength of currents, transport distance

Mudcracks: wet to dry conditions

Identify the depositional environment of common chemical and biochemical sedimentary rocks (rock salt, travertine, coal, chalk, limestone).

Chemical sedimentary rocks: Precipitated from a solution (ex. Sea water, ground water, lake water, hot spring) as a result of changing physical or chemical conditions

Rock salt: precipitation of dissolved minerals when water evaporates

Travertine (limestone): precipitation of minerals from chemical-rich waters

Biochemical sedimentary rocks: living organisms cause minerals to be precipitated from solution → forming shells/skeletons, lithification of the skeletons/shells

Chert (silica): lithification of silica shells

Limestone (calcite)

Remains of dead plants/organisms (coal, oil shale)

Transgression

sea level rises

Regression

sea level lowers

Explain the difference between the brittle and ductile zones in Earth, and at roughly what depth the transition takes place.

Brittle-ductile transition: 15-20 km into earth's surface

Brittle: low temperature, low pressure

Shallow: minerals show little change in composition

Ductile: higher temperature, higher pressure

Deep: minerals may recrystallize, new minerals grow

Crust and mantle fall below this transition

Explain the process of metamorphism in general terms (i.e. what causes it to happen?)

- Changes in mineral composition and texture that can occur in any solid rock

- Changes due to increasing temperature and/or pressure and/or the presence of high temperature fluids

Describe the ways in which rocks respond to metamorphism (Ex., recrystallization, neocrystallization, foliation, etc.)

Responses of rock:

Grow new crystals → new mineral

Grow larger crystals and/or rotation of minerals to form a foliation

Identify the range of temperatures in which lithification, metamorphism, and melting likely to occur.

lithification/weathering: effect of temperature overcomes effect of pressure at this point

contact metamorphism

metamorphism due to high temperature

regional metamorphism

metamorphism due to high temperature and high pressure

Slate

fine-grained, foliated, parent rock is shale

Schist

coarse-grained metamorphic rock, foliated, formed by mudstone/shale, regional metamorphism, medium grade

Gneiss

foliated, high grade, regional metamorphism, foliation,

Marble

non-foliated, metamorphosed limestone

Quartzite

hard, non-foliated metamorphic rock which was originally pure quartz sandstone. Regional metamorphism

Where is regional metamorphism likely to occur?

subduction zones

Where is contact and hydrothermal metamorphism likely to occur?

divergent boundaries

Explain how magma composition controls the explosiveness of a volcanic eruption.

viscosity = resistance to flow

Eruption style is affected by volatile content and viscosity of magma

- felsic/intermediate: explosive eruption

- Mafic: effusive eruption

Stratovolcanoes

Tephra (volcanic ash. debris)

Lahars (volcanic ,mudflowers)

Pyroclastic flows

Shield Volcanoes

lava (lava flows, cinder cones)

pyroclastic flow

Hot gases & ash, travel at 60 mph, around 700 degrees C

Lahars

10-20mph, debris mixes w/ water in streams or from melting ice

Volcanic Hazards

- Shield volcanoes have a shield-like shake, typically very large in area but their cones have a smoother, lower profile than composite volcanoes

-They are shaped this way because their lava flows are made of basaltic magma, which has lower viscosity than the lava from composite volcanoes

Determine the risk of volcanic hazards for a location if provided information regarding its proximity to a certain type of volcano.

Escaping gases drive volcanic eruptions

- How easily gases escape from magma is controlled by magma viscosity (A function of temperature and composition)

- High viscosity = hard to escape

- Low viscosity = easy to escape

Sketch and label normal fault, reversed fault, strike-slip fault.

see diagrams on study guide

List the three types of seismic waves and their relative velocities.

- P-Waves: or compressional wave, is a seismic body wave that shakes the ground back and forth in the same direction and the opposite direction as the direction the wave is moving; small jolt/light shaking or not felt

- S-Wave: or shear wave, is a seismic body wave that shakes the ground back and forth perpendicular to the direction the wave is moving; larger jolt/strong shaking

- Surface Waves: a seismic wave that is trapped near the surface of the earth; rolling motion

Explain the difference between earthquake magnitude and intensity.

Intensity refers to the degree of ground shaking at that locality; effect on people and buildings

Magnitude is a number that represents the amount of energy released from the seismic source, based on a measurement of the amplitude of ground shaking as recorded by a seismometer

angular uncnformity

an unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers. The whole sequence may later be deformed and tilted by further orogenic activity.

Disconformity

a break in a sedimentary sequence that does not involve a difference of inclination between the strata on each side of the break.

Nonconformity

A nonconformity exists between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock.

Know the age of the Earth and what this age is based on

Earth is 4.543 billion years old and is based on the relative age of rocks on earth.(Radioactive decay of isotopes has helped determine the relative age of rocks.

Calculate the age of a rock given information on the radioactive isotopes within the rock (make sure you can answer all the clicker questions).

If a rocks halflife is 1 million years and it has 1000 parent isotopes, how many parent isotopes are left after 3 half lives? 250

Determine the best radioactive to use when trying to date a rock, given the half-lives of various isotopes and a guess for the age of the rock.

The Key for these questions is looking for an element that's half life is most similar to that of the rock you are attempting to find the age of.

Describe the basis for the Geologic Time Scale.

check study guide for diagram

Describe the differences between the Precambrian, Paleozoic, Mesozoic, and Cenozoic divisions of the geologic timescale with respect to the global continental configuration, major species, and changes to atmospheric composition.

Precambrian-

Paleozoic- "ancient life" from 542Ma-251Ma life diversified rapidly

Mesozoic- "middle life" from 251Ma-65.5Ma age of dinosaurs.

Cenozoic- "recent life" from 65.5Ma-Present The age of Mammals.

List the major gases found in Earth's atmosphere and their relative proportions.

Earth's atmosphere is composed of 78% nitrogen, 21% Oxygen and 1% other gasses.

Describe and quantify the greenhouse effect, and list three major greenhouse gases (water vapor, CO2 and methane) in the atmosphere

- Greenhouse effect: Multiple absorption and reemission essentially trap a large amount of longwave radiation on earth.

- 3 Main greenhouse gasses:

Water Vapor: 95%

CO2: 3.6%

Other: 1.4%

- Methane is part of "other" however because water vapor makes up the majority of the atmosphere it appears to not make a substantial difference when in fact it does.

Describe reasons why Earth is hospitable to life, but other solar planets are not.

-Perfect distance from the sun

- Thickness and composition of the atmosphere

- Right chemical ingredients for life (carbon water)

- Alive planet supports cycling of elements.

Sketch the conceptual model of hydrologic cycle on land to show main reservoirs and fluxes

check study guide for diagram

Identify braided stream and meandering stream.

Braided Stream: Steep gradients, Coarse sediment, Shallow channel, Near mountains +/or glaciers,Generally no floodplain

Meandering Stream: Low gradients, fine sediment, deep channel, low elevations, floodplain.

Describe how stream flow characteristics change as a river flows downstream

As water moves downstream stream flow characteristics change as the majority of the discharge goes from headwaters to the mouth.

Draw a simple hydrograph showing how discharge looks like following a storm (time lag of the peak flow).

On lecture 22 ( picture wouldn't copy)

Interpret a graph of flood discharge vs. recurrence interval/yearly probability.

Recurrence interval= # years/# occurrences

Describe two major impacts of humans on hydrological cycle.

Urbanization increases flood risk as runoff is much more likely.

Climate related contributions of increasing sea level greatly affects hydrological cycle.

Describe how the ground water is discharged and recharged

Groundwater discharge is the term used to describe the movement of groundwater from the subsurface to the surface. There is natural discharge which occurs into lakes, streams and springs as well as human discharge, which is generally referred to as pumping.

Groundwater recharge or deep drainage or deep percolation is a hydrologic process where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer.

Explain what is water table.

The top of the saturated zone is the water table. Porosity (spaces between earth materials that can be filled with water) determines where water goes. (high porosity would be loose clay particles while high would be interlocked crystals in granite. Permeability also a determinant as a high permeability would be many fractures in granite while low permeability would be like compacted clay (shale)