Geology Exam #1

oWhat observations support there being distinct layers in the earth?

• Seismic waves (earthquakes

• volcanos (brings rock/minerals from deep mantle)

What observations support the core being iron?

• Earths magnetic field, needs a metal core to work

• dense material goes down with gravity

What observations support the mantle being made of silicate minerals?

• dense minerals like olivine and garnet are found there

• Silicon and oxygen formed them during subduction

What observations support continental drift

• Matching fossils and from the same age on diff. continents

• Coasts and mountain ranges line up (gps shows that)

• Seafloor is spreading at mid ocean ridges

Theory

A tested explanation built on a lot of evidence and repeatedly tested hypotheses.

Can a theory be wrong? If so, give an example.

Yes, it can be proven wrong when new evidence contradicts it. Ex: Wegener’s explanation for how the continents actually moved was wrong.

Give an example of a geology model

block diagrams: model that used a 3D representation to show subsurface structures like faults and layers.

Boundary between crust and mantle

Moho

Boundary between core and mantle

CMB

Layers in the lithosphere(solid)

Crust and top of mantle

Layers in Asthenosphere

Middle layer of mantle

Ductile definition

able to be deformed without losing toughness; pliable, not brittle.

Convection in what layer causes plate movement?

Upper mantle

The outer core is ____ while the inner core is _____

Liquid, solid

Why is the outer core liquid but the inner core is solid?

The outer core’s pressure is not enough to beat the high temp.

What layers contain silicates?

Crust and mantle

Geodynamo

the liquid outer core sustains the magnetic field through motion of the molten metal

What leaves “stripes” on ocean floor of magma with iron in it

magnetic pole switch.

What makes the plates move?

internal heat of the Earth and gravity

What happens to a plate as it subducts?

sinks into the Earth's mantle due to its density, forming a deep ocean trench and a subduction zone

What is the Wilson Cycle?

Describes the evolution of tectonic plates and plate interactions

Converging boundaries

Come together/denser subducts

Diverging boundary

Splits apart/ new plate created

Vitreous

a luster, shiny like glass

H8, can be many colors, vitreous luster, white streak, extremely good cleavage in one direction (makes very flat surfaces), forms prisms that are often octagons

Topaz

H2.5, grey/silver color, metallic luster, grey streak, grows in cubes/cubic cleavage. Dense

Galena

H2.5-3, yellow color, yellow streak, metallic luster, dense

Gold

H7, brown color, white streak, vitreous or dull luster, poor cleavage, forms as
crossed prisms

H7, brown color, white streak, vitreous or dull luster, poor cleavage, forms as
crossed prisms

H7, brown, forms as crossed prisms

Staurolite

H2.5 can peel away in sheets

Muscovite mica

H2.5-3, orange/brown color, orange/brown streak, metallic luster but can

tarnish

Copper

H2-6, red/grey/silver/black color, brick red streak, luster varies

Hematite

Most dangerous volcano hazard

Pyroclastic flow

H6, pink/orange/salmon color, vitreous luster,

Orthoclase feldspar

H3.5-4, colorless/pale colors

Dolomite

pink extrusive felsic rock?

Rhyolite

intermediate extrusive rock?

Andesite

black intrusive mafic rock

gabbro

has a lot of orthoclase feldspar, quartz, and muscovite mica

Ryholite

Scoria texture?

Vesicular

Most common rock in mantle? It’s green and ultramafic

peridotite

Intrusive felsic rock?

Granite

Polymorph example

Diamond/graphite

igneous intrusion that is a vertical flat sheet is called a

dike

an amphibole has a chemical structure where the silicate ions are in a

double chain

What is the most common mineral group in both the crust and the mantle?

Silicates

Metamorphic types

foliated / nonfoliated

hy are clay minerals like kaolinite easily physically weathered, but resistant to chemical weathering?

They were already chemically weathered in their formation.

Which type of igneous rock would be most easily chemically weathered?

Mafic

metallic Shiny rocks most likely

Metamorphic

inthe context of sedimentary environments, if a sediment is unsorted, it means that the pieces of sediment have a wide range of

sizes

Extrusive means cooled _____

quickly

Intrusive cools ______

slowly

If you find an area of rock with fine grained sediments, symmetric ripples, organics, mudcracks and

bioturbation structures, it most likely formed in which of these sedimentary environments?

a) a desert b) a river c) a glacier d) a tidal flat

Tidal flat

word “granoblastic” refers to a(n)

a) large, flawless crystal b) category of metamorphic rock c) type of mineral fracture

d) sedimentary structure found in deserts e) intermediate igneous rock

category of metamorphic rock

Which type of plate boundary has the most volcanoes?

Converging

Is a chemical sedimentary rock softer or harder than an igneous rock?

Softer

What does good cleavage mean?

breaks with flat surfaces

If an igneous rock has a porphyritic texture, it means that it is

a) extrusive b) intrusive c) both d) neither

both

If sedimentary rock is showing graded bedding, it means that

a) the ripples are symmetric b) the sediment is sorted by size c) there are glacial grooves

d) the rock layers are flat and horizontal e) the rock layers are flat but tipped at an angle

sediment is sorted by size

What are two ways you could tell graphite and apatite apart?

• hardness/graphite scratched by nail, apatite not

• Streak/ dark and apatite white

• Luster/ metallic, apatite glass like

What layer gives mafic magma

upper mantle

High silica content will crystalize ______

first

High calcium content will crystalize _____

last

Flux- induced (type of melting), what does water do and what boundary is it near?

water lowers melting temp, increases melting and convergent boundary

Decompression (melting process) reduces ____, increases_____, most common at _____ boudnary

pressure, melting, divergent

Lava type (Rhyolitic- felsic) description

thick