chapter 14: Geology Flashcards
earth core
interior composed of dense, intensely hot metal, mostly iron. generates magnetic field enveloping the earth
earth mantle
hot, pliable layer surrounding the core, less dense than the core
earth crust
cool, lightweight, brittle, outermost layer; floats on top of the mantle
tectonic processes
upper layer of mantle contains convection currents that break overlying crust into tectonic plates that slide slowly across earth’s surface
when tectonic plates slide
ocean basins form where continents crack and pull apart, magma (molten rock) forced up through the cracks form new oceanic crust piles up underwater mid-ocean ridges
earthquakes
caused by grinding and jerking as plates slide past each other
subduction zones
markedby deep ocean trenches
mineral
naturally occurring inorganic, solid element of compound with definite chemical composition and regular internal crystal structure
rock
solid, cohesive, aggregate of one or more minerals, characteristic mixture of minerals, grain sizes, and ways in which the grains are mixed and held together
rock cycle
cycle of creation, destruction and metamorphosis
major rock classifications
igneous, sedimentary, metamorphic
igneous rocks
most common type in earth’s crust, solidified from magma extruded onto surface from volcanic vents, cooling magma creates basalt, granite
metamorphic rock
preexisting rocks modified by heat, pressure, and chemical agents, chemical reactions alter composition and structure as they are metamorphosed, marble, slate
mechanical weathering
physical break-up of rocks into smaller particles without a change in chemical composition
chemical weathering
selective removal or alteration of specific components that leads to weakening and disintegration of rock, oxidation and hydrolysis
sedimentation
deposition of particles of rock transported by wind, water, ice and gravity until they come to rest in a new location
sedimentary rock
deposited materials that remain in place long enough or covered with enough material for compaction, sandstone and shale, shaped by erosion, can be formed from crystals
geomorphology
study of processes that shape the earth’s surface and the structures they create, humans shape more than other processes minus plate tectonics
economic mineralogy
study of minerals that are valuable for manufacturing
metals
consumed in greatest quantities by world industry, iron most often
gemstones and precious metals
monetary value bankrolls despots, criminal gangs, terrorism, inhumane labor conditions
sand and gravel
greatest volume and dollar value, brick and concrete, sandblasting, glass production
extraction
disturbance or removal of land surface, 80,000 metric tons of dust, toxic air pollutants, chemical and sediment runoff, contaminated freshwater with acid, arsenic, heavy metal
placer mining
hydraulically washing out metals deposited in stream bed gravel by using water cannons to blast away stream beds
underground mining
tunneling into mineral seams, dangerous, natural gas explosions, collapse of tunnel, water seeping into mines dissolves toxic minerals contaminating water, fires burn for years
open pit or strip mining
50% US coal, creates huge holes with fill with contaminated groundwater, surface material is left long ridges called spoil banks
surface mining control and reclamation act
requires better restoration of strip-mined lands, difficult and expensive, more that $10,000/hectare
mountaintop removal
ridge tops removed to access a coal bed, material from top of mountain is crushed and dumped into river valleys burying streams in toxic substances
smelting
roasting ore to release metals, major source of air pollution
heap-leach extraction
crushed ore piled in large heaps and sprayed with a dilute alkaline cyanide solution which percolates through pile to dissolve the gold
recycling
aluminum must be extracted from bauxite by electrolysis which is energy expensive, commonly recycled plantinum, gold, silver, copper, lead, iron, steel
reduce metal consumption by…
using new materials or new techniques like, metal pipes replaced by plastic pipes, metal wires replaced by fiber optics, steel replaced by polymers, aluminum, ceramics, and new alloys
geologic hazards
asteroid impact led to extinction of dinosaurs, floods take the greatest number of lives, wind causes most property damage, earthquakes
gradual movement
called creep or seismic slip, when friction prevents creep, stress builds up until eventually released with a sudden jerk
epicenter
point at which first movement occurs in an earthquake
earthquakes cause more damage…
when construction is poor
tsunami
generated by earthquakes, tidal wave
what are the sources of most of the earths crust?
volcanoes and undersea magma vents
volcanoes
fertile soils are weathered volcanic material, 500 million people live in danger zones
nuees ardentes
buring cloud, deadly clouds of hot gas and ash like those that destroyed pompeii, volcanic dust and sulfur emissions reduce sunlight and temperature around globe
landslides
example of mass wasting, geologic material are moved downslope from one place to another, speeds vary
damage caused by landslides
road construction, forest clearing, cultivation, and building on steep, unstable slopes increase the frequency
