Geosciences Midterm

Plate Tectonic Theory

The recognition that the lithosphere is divided into mobile, rigid plates that move over the athenosphere

Who was Alfred Wegener? What were his three pieces of evidences? How did they prove anything?

Proposed the idea of continental drift, fit of all the continents (they all look like puzzle pieces), glacial data (glaciers pick up rocks that leave striations, there are matching striations across continents and evidence of glaciers in tropical areas), fossil distributions (there are fossils of animals found in climates they could have never survived on spread across the continents)

Why were Wegener’s theories rejected

He couldn’t explain why or how (how it moved with the different crust densities, couldn’t explain why they moved at all)

Who was Harry Hess? What proved his idea?

Seafloor spreading and paleomagnetism

What is paleomagnetism

Iron rich material will crystallize to align with magnetic north, polar wander paths show the magnetic north moving, the poles sometimes reverse

Why do plates move

Mantle convection, ridge-push, slab-pull

What is a divergent plate boundary and what is a real life example

Tensional stress, move away, Mid-Atlantic Ridge, East Pacific Ris

What are the geological features of a divergent plate boundary

Mid ocean basins, rift valleys

What is an oceanic-oceanic convergent plate boundary and what is a real life example

Compressional, older below newer (denser), Japan

What is a oceanic-continental convergent plate boundary and what is a real life example

Compressional, ocean under continental, Andes Mts./Cascade Range

What is a continental-continental convergent plate boundary and what is a real life example

Compressional, less dense goes under but doesn’t subduct, Himalayan Mountains

What are the geological features of a oceanic-oceanic convergent plate boundary

Island arc, oceanic trench, back-arc basin

What are the geological features of a oceanic-continental convergent plate boundary

Volcanic arc, oceanic trench, mountain belt

What are the geological features of a continental-continental convergent plate boundary

Suture zone, mountain belt

What are the geological features of a transform plate boundary

Step over faulting at mid-ocean ridges, lateral movement

What is a transform plate boundary and what is a real life example

Shear, slide past, San Andres Fault System

What are hot spots? How do they help us track plate movement? What are real life examples?

Plumes of magma from cracks in the mantle, they stay but new volcanoes emerge, Hawaii and Iceland

What is a mineral

A naturally occurring solid, with a definite chemical compound, and crystalline structure

Three kinds of crystals

Euhedral, subhedral, anhedral

Cleavage v fracture

Clean v ragged

Basal, cubic, and rhombic cleavage meanings

1 like sheets, 3 at 90 degrees, 3 not at 90 degrees (often 60/120)

Name the 7 non-silica groups (Nebula’s Clever Orb Holds Secret Space Plans)

Native elements, carbonates, oxides, halites, sulphates, sulfides, phosphates

Magma v lava

Inside v out

Two kinds of igneous rock

Intrusive v extrusive

How are igneous rocks described

Composition and texture

What are the percentages of silica felsic, intermediate, mafic, and ultramafic

+65%, 55-65%, 45-55%, <45%

How does color help signify igneous composition

lighter=more silica, darker=less silica

What is phaneritic v aphanitic

Coarse (cooled slow) v fine (cooled fast)

What is porphyritic texture

Contains both, has big grains called phenocrysts

What is fragmental texture

Debris welded together in an explosion

How does melt form

Decompressional melting (less pressure), flux melting (substances that evaporate easily break bonds, heat transfer

What classifies magma

Source rock and melting process

What is viscosity?

Resistance to flow (high=high silica, low=low silica)

Factors to rate of magma cooling

Depth of intrusion, shape and size, circulating groundwater

Igneous intrusive rock settings (Pumbaa dances so loudly)

Plutons (large cooled magma chambers), dikes (vertical), sill (horizontal), laccolith (lateral built up into blister)

Igneous extrusive settings

Volcanoes

What are accretionary prisms

The stack of sediments rubbed off the top of the subducting plate

Types of lava

Rhyolitic/andesitic - si rich, basalt - si poor

What are 4 products of eruptions (Lokis glorious power descends)

Lava, gas release, pyroclastic debris, and debris flows/lahars

What is a lahar

Flash flood essentially when form ash-rich debris gets wet

Crater v caldera

Volcano portion around the vent that collapses v after volcano erupts when more pieces collapse because no more magma holds it up

Shield volcanoes - eruption type, lava comp, real life example

Broad gentle slope, effusive, basaltic, Mauna Loa/Kilauea

Stratovolcanoes volcanoes - eruption type, lava comp, real life example

Large steep sided consisting to inter-layered lava tephra and volcanic debris, explosive, andesitic/rhyolitic, Mt. Fuji

Cinder cone volcanoes

1 event, just a crack, violent but foes not hold up, basaltic flows out fissure cracks and pyroclastic shoots out of top

Lava domes

Accumulation of si-rich volcanic crack and obsidian, highly unstable because the rock clogs the eruption

Supervolcanoes

Eruptions that eject over 1000km³ of debris (largest: 73000 BCE, Indonesia - 2800 km³)

Mid ocean ridges

Basaltic lava is produced, products of this volcanism covers 70% of Earth’s surface

Continental rifts

Basaltic fissure eruptions, development of cinder cones, and explosive rhyolitic volcanism

Flood basalts

Extraordinarily large amounts of low-viscosity basaltic lava erupts out of fissures and spread out into thin sheets

Gypsum (group, hardness)

Sulfate, soft

Microcline (cleavage, color, characteristics, group)

2 planes @ 90, salmon pink, striations, silicate

Muscovite (cleavage, color)

1 cleavage direction (sheets), translucent/greenish-brown

Biotite (cleavage, color)

Black but same as muscovite

Talc (characteristics, hardness)

Soapy, greasy, 1 hardness

Pyrite streak

Dark gray or black (glittery)

Quartz (color, hardness, breaks how, group)

All colors, high hardness bc of tetrahedra bonds, fractures, silicate

Na plagioclase feldspar (color, cleavage, characteristic)

White/cream, 2 planes @ 90, striations

Pyroxene (cleavage)

2 directions @ 90

Amphibole (cleavage)

2 directions @ 90

Calcite (characteristics, hardness, color, cleavage, group)

Strongly reacts to HCl, 3 hardness, white/transparent, carbonate, rhombic

Galena (group, cleavage, density)

Sulfide, cubic, very heavy for size/dense

Dolomite (group, characteristics)

Carbonate, light reaction to HCl

Quartz sandstone (group, size, sorted, angularity/sphericity, location)

Sedimentary, sand sized, well sorted, rounded, found in streams beaches and deserts

Shale (group, size, sorted, angularity/sphericity, location)

Sedimentary, clay sized, well sorted, rigid, low energy environments lake beds deep marine

Conglomerate (group, size, sorted, angularity/sphericity, location)

Sedimentary, pebble sized, poorly sorted, rounded, headwaters of streams/high energy environments

Siltstone (group, size, sorted, angularity/sphericity, location)

Sedimentary, silt sized, well sorted, rigid, low energy, floodplains lakes and deltas

Breccia (group, size, sorted, angularity/sphericity, location)

Sedimentary, pebble sized, poorly sorted, rigid, alluvial fans and high energy environments

Granite (group, comp, setting, texture, comp specific)

Igneous, comp: felsic, setting: intrusive, texture: phaneritic, comp specific: quartz microcline Na plagioclase muscovite biotite

Peridotite (group, comp, setting, texture, comp specific)

Igneous, comp: ultramafic, setting: intrusive, texture: phaneritic, comp specific: olivine augite

Andesite (group, comp, setting, texture, comp specific)

Igneous, comp: intermediate, setting: extrusive, texture: phaneritic, comp specific: Na and Ca plagioclase hornblende biotite

Basalt (group, comp, setting, texture, comp specific)

Igneous, comp: mafic, setting: extrusive, texture: aphanitic, comp specific: Ca plagioclase, augite, hornblende, maybe olivine

Diorite (group, comp, setting, texture, comp specific)

Igneous, comp: intermediate, setting: intrusive, texture: phaneritic, comp specific: na and ca plagioclase, hornblende, biotite

Rhyolite (group, comp, setting, texture, comp specific)

Igneous, comp: felsic, setting: extrusive, texture: aphanitic, comp specific: quartz, microcline, na plagioclase, muscovite, biotite

Gabbro (group, comp, setting, texture, comp specific)

Igneous, comp: mafic, setting: intrusive, texture: phaneritic, comp specific: ca plagioclase, augite, hornblende, maybe olivine

2 vesicular… whats the difference

pumice and scoria, pumice is lighter=more si

Chert depositional environment

Deep marine in siliceous ooze, precipitates fom si-rich solution in terrestrial settings

Fossiliferous limestone depositional environment

shallow marine, coral reefs, carbonate shelves

Oolithic limestone depositional environment

High energy, shallow marine

4 steps of scientific method

Observation, hypothesis, theory, scientific law

Theory v scientific law

Theory - what you think after testing, law - what is true and unchanging

What does the big bang theory explain

The universe expanding from one singular point

What two factors influence an objects gravitational pull

Density and distance

What is responsible for igniting a star

Nuclear fusion reactions of hydrogen and helium

What happens when a star runs out of fuel

They collapse inward and explode in a supernova

Stellar nucleosynthesis

Heavier elements form as a byproduct of nuclear reactions

How do galaxies form

Nebula materials coming together in an accretionary disc

What does the Solar Nebula Theory explain

How our solar system was created

Differentiation

Separation of materials by density

3 layers of the Earth

Crust, mantle, core

Lithosphere v asthenosphere

Lithosphere - crust and upper mantle, iron-rich solid, behaves rigidly, little silica/oxygen v asthenosphere - same chemical comp as upper mantle, behaves like silly putty, moves the plates, mainly peridotite

Inner core v outer core

Inner - melted metals v outer - solid metals

What generates Earth’s magnetic field

Hot, spinning metals

What are the point of magnetic fields

Deflect solar winds, maintains the atmosphere

Atmosphere (allowed by what and how did it form)

Allowed by gravity, out gassing from volcanoes as Earth began to form

Hydrosphere/Crynosphere

All the water on Earth (cryno is ice)

Geosphere

Rocky portion, the Earth itself

Biosphere

Everything alive

Slate (category, protolith, characteristics, texture)

Metamorphic, shale, fine grained rock splits into parallel fragments), foliated

Slaty cleavage

Metamorphic rock breaks into sheets

Schist (category, protolith, characteristics, texture)

Metamorphic, shale, contains shiny muscovite (light) or biotite (dark) micas schistose pattern of foliation, foliated