EARTH SCIENCE

crust

solid rock, silicate

5-70 km thickness

mantle

silicate rock, mostly solid but flows slowly

~2,900 km thickness

outer core

iron + nickel

2,200 km thickness

inner core

iron + nickel

1,220 km radius

continental crust

granite (felsic), density: lower

thicker (30-70 km)

older

oceanic crust

basalt (mafic), higher density

thinner (5-10 km)

younger

lithosphere

the crust + the rigid upper mantle together form ___

brittle outer shell that makes up the tectonic plates

asthenosphere

the soft, partially molten mantle layer the plates “float” and slide on

tectonic plates

earth’s lithosphere is broken into large rigid pieces called

mantle convection

hot material rises, cools, sinks, creating circulation currents that drag plates along

continental drift

Alfred Wegener

• continents fit together like puzzle pieces (e.g America + Africa); matching fossils and rock types appear on now-separated continents

seafloor spreading

new crust forms at mid-ocean ridges and spreads outward, confirmed by magnetic striping (symmetrical bands of normal/reversed magnetic polarity in seafloor rock) and age of seafloor rock (youngest near ridges, oldest near continents

divergent

plates move apart

• mid ocean ridges, rift valleys, new crust formation (e.g., mid-atlantic ridge, east african rift)

convergent

plates move toward eachother

• subduction zones, deep ocean trenches, volcanic arcs, mountain ranges (e.g., Andes, Himalayas, Philippine trench)

transform

plates slide past eachother

• fault zones, earthquakes, no major crust creation/destruction (e.g., San Andreas fault)

oceanic-continental

denser oceanic plate subducts under continental plate - volcanic arc - trench (Philippine trench)

oceanic-oceanic

one oceanic plate subducts under the other - island arcs (marianas, parts of the philippines/japan)

continental-continental

neither subducts (similar density) - crust crumples upward - massive mountain ranges (himalayas from india - eurasia collision)

pacific ring of fire

the Philippines sits on the _______ where the Philippine sea plate, eurasian plate, and several microplates interact

igneous rock

formed from cooled magma/lava

intrusive (plutonic)

cools slowly underground - large crystals (granite)

extrusive (volcanic)

cools quickly at the surface - small/no crystals (basalt, obsidian, pumice)

sedimentary rock

formed from compacted / cemented sediment

• often shows layering (strata) and may contain fossils

metamorphic rock

formed by heat and pressure transforming existing rock (without melting)

• often shows foliation (banded texture) from directional pressure

weathering

breaking rock down in place

frost wedging

water seeps into cracks, freezes, expands, splits rock

thermal expansion / contraction

repeated heating / cooling (common in deserts)

• stresses rocks until it cracks

exfoliation

outer rock layers peel off, often after pressure release (after overlying rock erodes away)

abrasion

rock-on-rock grinding from wind, water or ice carrying particles

biological (root-wedging)

plant roots grow into cracks and pry rock apart

oxidation

minerals react with oxygen (ex. iron rusting)

hydrolysis

minerals react with water, often forming clay

carbonation

CO2 dissolves in water to form weak carbonic acid which dissolves limestone - this is the basis of karst topography

dissolution

minerals dissolve directly in water (especially salts)

chemical weathering

dominates in warm, wet climates (more water + heat speeds reaction)

physical weathering

dominates in cold or dry climate (freeze-thaw cycles, less water for chemical reactions)

erosion

the action of surface processes that removes, soil, rock, or dissolved material from one location on the Earth’s crust and then transports it to another location where it is deposited

deposition

the laying down of sediment carried by wind, flowing water, the sea or ice

fold mountains

crust compressed and buckled upward (himalayas, andes) typically at continental collision zones

fault-block mountains

large blocks of crust uplifted / dropped along faults (sierra nevada)

volcanic mountains

built from erupted material

plateaus

large, flat, elevated areas - can form from uplift without folding, or from layered lava flows

rift valleys

long depressions formed where crust pulls apart

v-shaped valleys

upper river course, fast erosion downward

floodplains

flat, fertile land flooded periodically

deltas

sediment deposited where a river meets a still body of water

alluvial fans

fan-shaped deposits where a river exits steep terrain onto flatter ground

erosional

sea cliffs, sea caves, sea arches, sea stacks, wave-cut platforms

depositional

beaches, sandbars, spits, barrier islands, lagoons

karst landforms

• sinkholes, caves, caverns, underground rivers

• forms where slightly acidic water dissolves carbonate rock over time

sand dunes

deposition

• desert pavement (erosion removes fine particles, leaving coarse ones)

loess

find wind-deposited sediment, often very fertile soil

shield volcano

broad, gently sloping

• effusive, low viscosity lava

• mauna loa

composite / stratovolcano

steep, conical, layered

• explosive, alternating lava / ash

• mayon pinatubo

cinder cone

small, steep-sided

• explosive, short lived

• paricutin

caldera

large depression

• forms after massive eruption / collapse

• taal volcano

earthquake

sudden release of energy along a fault (a fracture in rock where movement occurs), usually due to built-up stress from plate movement

normal fault

one block drops relative to the other (tension)

• divergent

reverse fault

one block pushed up over another (compression)

• convergent

strike-slip fault

blocks slide horizontally past each other

• transform

magnitude

energy released

• richter scale

intensity

observed effects

• PEIS

focus

the point underground where the rupture starts

epicenter

the point on the surface directly above the focus

mass wasting

movement of rock/soil downslope due to gravity, often triggered by heavy rain, earthquakes, or human activity

landslide / rockslide

rapid downslope movement of rock debris

slump

rotational slipping of a coherent mass along a curved surface

creep

very slow, gradual downslope movement of soil

mudflow / lahar

fast-moving mixture of debris and water

aquifer

rock/sediment that can store and transmit usable groundwater

water cycle

evaporation - condensation - precipitation - runoff/infiltration - back to oceans

relative dating

determining the order of events using principles like superposition (older layers are beneath younger ones) and cross-cutting relationships (a feature that cuts across rock layers is younger than those layers

absolute dating

determining actual age using radiometric dating (measuring decay of radioactive isotopes)

• carbon-14

mineral criteria

naturally occuring, inorganic, solid, definite chemical composition, oderly crystalline structure

geosphere

solid, non-living portion of the earth