Geology & Earth Resources - Chp 12 ENSC

Core

interior composed of dense, intensely hot metal, mostly iron. Generates magnetic field enveloping the earth

Mantle

hot, pliable layer surrounding the core. Less dense than core

Crust

cool, lightweight, brittle outermost layer. Floats on top of mantle

subduct

When an oceanic plate collides w/ a continental landmass, the continental plate will ride up over the seafloor & the oceanic plate will ___ down into the mantle where it melts

subduction zones

Deep ocean trenches mark ___

tectonic plates

Upper layer of mantle contains convection currents that break overlying crust into a mosaic of

Magma

(molten rock) forced up through the cracks forms new oceanic crust that piles up underwater in mid-ocean ridges

mid-ocean ridges

Magma (molten rock) forced up through the cracks forms new oceanic crust that piles up underwater in ___

Mineral

a naturally occurring, inorganic, solid element or compound w/ a definite chemical composition & regular internal crystal structure

Metals

(such as iron, copper, aluminum, or gold) come from mineral ores, but once purified, metals are no longer crystalline & thus are not minerals

Rock

a solid, cohesive, aggregate of one or more minerals

rock cycle

Rocks are part of a relentless cycle of formation & destruction

Igneous rocks

are solidified from hot, molten magma or lava

Most common type of rock in Earth’s crust

Metamorphic rocks

form from the melting, contorting, & recrystallizing of other rocks

Preexisting rocks modified by heat, pressure, & chemical agents

Sedimentary rocks

are formed when loose grains of other rocks are consolidated by time & pressure
Deposited materials that remain in place long enough, or are covered w/ enough material for compaction, may again become rock

Weathering

the breakdown of rocks by air, water, temperature changes, or chemical agents

Mechanical weathering

physical break-up of rocks into smaller particles w/out a change in chemical composition

Chemical weathering

 selective removal or alteration of specific components that leads to weakening & disintegration of rock

Sedimentation

deposition of particles of rock transported by wind, water, ice & gravity until they come to rest in a new location
Deposited materials that remain in place long enough, or are covered w/ enough material for compaction, may again become rock

Economic mineralogy

the study of resources that are valuable for manufacturing & trade

Gemstones & Precious Metals

Their monetary value bankrolls despots, criminal gangs, terrorism, inhumane labor conditions

Sand & gravel

greatest volume & dollar value
Brick & concrete construction, paving, sandblasting
Glass production

High-purity silica sand

our source of glass

Limestone

mined & quarried for concrete, crushed for road rock

Halite or rock salt

used for water softening & ice melting on winter roads in northern areas or refined for use as table salt

Gypsum

(calcium sulfate) now makes our plaster wallboard

Sulfur

mined for sulfuric acid in industry & batteries

Lithium

found in salt flats, is crucial for batteries in electronics & electric vehicles

Rare Earth Elements/REEs

make possible our small cell phones, high-efficiency lightbulbs, hybrid cars, superconductors, high-strength magnets, lightweight batteries, lasers, energy-conserving lamps, & a variety of medical devices

Placer Mining

hydraulically washing out metals deposited in streambed gravel by using water cannons to blast away stream beds

Underground mining

tunneling into mineral seams is very dangerous

Open-pit or strip mining

extracts large metal ores & minerals, but groundwater contamination in the pits poses environmental challenges

spoil banks

Surface material is left in long ridges called ___ because these do not contain topsoil, there often is no vegetation for many yrs

mountain removal

Mining companies have recently begun to remove Appalachian coal via ___

Ridge tops are removed to access a coal bed. The material from the ridge top is crushed & dumped into adjacent river valleys, burning streams in toxic substances

Surface Mining Control & Reclamation Act (1977)

requires better restoration of strip-mined lands, especially if land classes as prime farmland

Smelting

roasting ore to release metals

Heap-Leach Extraction

crushed ore piled in large heaps & sprayed w/ a dilute alkaline cyanide solution which percolates through the pile to dissolve the gold

Minimills

which use scrap steel & iron, are more energy-efficient & produce about half of all US steel, w/ recycling rates for iron & steel at 80-90%

Asteroid impact

led to extinction of dinosaurs

Floods

___ take the greatest number of lives

normal events that cause dmg when ppl get in the way

Wind

___ causes the most property dmg

Earthquakes

sudden movements of the Earth’s crust that occur along faults where one rock mass slides past another
often occur at tectonic plate boundaries, especially where one plate is subducted beneath another, but they can also happen in the center of continents

Gradual movement

called creep or seismic slip
When friction prevents creep, stress builds up until eventually released w/ a sudden jerk

epicenter

Point at which first movement occurs is called the

Tsunamis

triggered by underwater earthquakes, can travel at speeds up to 1,000 kph, causing massive destruction when they reach shore, as seen in the 2011 Japan tsunami

Stages of tsunamis evolution

generation, propagation, inundation

Nuees ardentes

deadly clouds of hot gas & ash like those that destroyed Pompeii, temperatures exceed 1000 °C, they move at 60 mph & can kill in minutes

floodplains

As rivers carve & shape the landscape, they build broad ___ lvl expenses that are periodically inundated

Barrier islands

thin, sandy islands that protect mainland areas from ocean storms, but they are vulnerable to beach erosion
occurs on all sandy shorelines b/c the motion of the waves is constantly redistributing sand & other sediments

The Coastal Barrier Resources Act of 1982

aimed to limit development on sensitive islands, but legal challenges have hindered its enforcement

mass wasting

Landslides are examples of ___ which geologic materials are moved downslope from one place to another

Landslides

sudden collapses of hillsides, often triggered by storms, logging, construction

Soil creep

a slow, gradual movement of material downhill