Geology Exam 3

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Chapters 10, 14-15complete, 16-18complete, 19

ENERGY

provides the capacity to do work, to cause something to happen, or to cause change in a system.

energy resources

any item that can be employed for a useful purpose, more specifically something that can be used to produce heat, power muscles, produce electricity, or move vehicles.

fossil fuels (fuel)

(oil, gas, and coal) - combustible materials derived from organisms that lived in the past. Specifically they are matter that stores energy in a readily usable form.

sources of energy on Earth

(1) energy generated by nuclear fusion in the Sun and transported to Earth via electromagnetic radiation; (2) energy generated by the pull of gravity; (3) energy generated by nuclear fission reaction; (4) energy that has been stored in the interior of the Earth since the planet's beginning; (5) energy stored in the chemical bonds of compounds.

energy from the Sun

source of energy on Earth; (solar energy) can be converted directly to electricity, using solar panels, or it may used as heat water or to warm a house.

energy from gravity

source of energy on Earth; the gravitational attraction of the Moon, and the Sun, causes ocean tides of the sea surface. The flow of water in and out of channels during tidal changes can drive turbines.

both solar energy and gravity

source of energy on Earth; solar radiation heats the air, which becomes buoyant and rises. Thus, gravity causes cooler air to sink, the resulting air movement, wind, can power sails and windmills. When water condenses, it rains and falls on the land, where it accumulates in streams that flow downhill in response to gravity. This moving water powers waterwheels and turbines.

energy via photosynthesis

source of energy on Earth; green plants absorb some of the solar energy that reaches Earth's surface. With the aid of chlorophyll, plants produce sugar through a chemical reaction called photosynthesis. Burning plant matter in a fire releases potential energy stored in the chemical bonds of organic chemicals. Wood burning produces energy, and recently plant material (biomass) from crops such as corn and sugar cane has been used to produce ethanol, a flammable alcohol.

energy from chemical reactions

source of energy on Earth; a number of inorganic chemicals can burn to produce light and energy, energy resulting from exothermic reactions. Researchers have been studying electrochemical devices, such as hydrogen fuel cells, that produce electricity directly from these reactions.

energy from fossil fuels

source of energy on Earth; oil, gas, and coal come from organisms that lived long ago, and thus store solar energy that reached the Earth long ago. Burning these fuels produces energy in the same way that burning plant matter does.

energy from nuclear fission

source of energy on Earth; atoms of radioactive elements can split into smaller pieces. During this process, a tiny amount of mass is transformed into a large amount of energy, called nuclear energy. This type of energy runs nuclear power plants and nuclear submarines.

energy from Earth's internal heat

source of energy on Earth; Earth's internal energy dating back to the birth of the planet, while some is produced by radioactive decay in minerals. This internal energy heats water underground, the resulting hot water when transformed to steam, provides geothermal energy that can drive turbines.

hydrocarbons

oil and natural gas consist of these chainlike or ringlike molecules made of carbon and hydrogen atoms. These are considered to be a type of organic chemical, so named because similar chemicals make up living organisms. Products composed of short chains of molecules tend to be less viscous (they can flow more easily) and more volatile (they evaporate more easily) than products composed of long chains. Thus, short-chain molecules occur in gaseous form at room temperature, moderate-length-chain molecules as liquids, and long-chain molecules occur in solid form as tar.

oil and gas formations

the primary sources of the organic chemicals in oil and gas are dead algae and plankton. When algae and plankton die, they settle to the bottom of a lake or sea. Because their cells are so tiny, they can be deposited only in quiet-water environments in which clay also settles, so typically the cells mix with clay to create an organic-rich, muddy ooze; to be preserved it must be deposited in oxygen-poor water. Eventually, the resulting ooze lithifies and becomes black organic shale which contains raw materials from which hydrocarbons eventually form.

source rock

organic shale is referred to as ____ ___. Contains the raw materials from which hydrocarbons eventually form. These rocks are always sedimentary.

kerogen

if organic shale is buried deep enough (2 to 4 km), it becomes warmer, since temperature increases with depth in the Earth. Chemical reactions slowly transform the organic material in the shale into these waxy molecules called ___. Shale containing this is called oil shale.

oil window

if oil shale warms to temperatures of greater than about 90C, the kerogen molecules break down to form oil and natural gas molecules. At temperatures over 160C, any remaining oil breaks down to from natural gas, and at temperatures over 250C, organic matter transforms into graphite. Thus, oil itself forms only in this narrow range of temperatures. For regions with a geothermal gradient of 25C/km, this window lies at depths of about 3.5 km to 6.5 km, whereas gas can survive down to 9 km. Thus, hydrocarbon reserves can only exist in the topmost 15 to 25% of the crust.

hydrocarbon reserve

a known supply of oil and gas held underground. Currently countries bordering the Persian Gulf contain the world's largest reserves.

hydrocarbon system

a particular association of - source rock, reservoir rock, migratory pathway, and a trap - along with the processes of hydrocarbon generation, migration, and accumulation that ultimately produce a reserve from a given source, a system called the ____ ___.

hydrocarbon generation

geologists refer to the organic-rich shale as a source rock because it is the source for the organic chemicals that ultimately become oil and gas. If black shale resides in the oil window, the organic material within transforms into kerogen, and then into soil and gas. This process is ..

reservoir rocks

any organic matter in an oil shale remains trapped among the grains and can't move easily. Thus to obtain oil, companies drill into these rocks which contain (or could contain) an abundant amount of easily accessible oil and gas, meaning hydrocarbons that can be extracted out of the ground. Rocks with high porosity and permeability are the best.

pores

to be a reservoir rock, a body of rock must have space in which the oil or gas can reside, and must have channels through which the oil or gas can move. The space can be in the form of open spaces, or ___, between clastic grains or in the form of cracks and fractures that developed after the rock formed.

porosity

in some cases, groundwater passing through rock dissolves minerals and creates space, this refers to the amount of open space in a rock.

permeability

refers to the degree to which pore spaces connect to each other. In a permeable rock, the holes and cracks (pores) are linked, so a fluid is able to flow slowly through the rock, following a tortuous pathway.

migration pathway

to fill the pores of a reservoir rock, oil and gas must first migrate (move) from the source rock into a reservoir rock, which they will do over millions of years of geologic time. Hydrocarbons migrate because oil and gas are less dense than water, so they try to rise toward the Earth's surface to get above groundwater. Natural gas, being less dense, ends up floating above oil, thus buoyancy drives oil and gas upward. Typically, a hydrocarbon system must have a good ___ ___, such as a set of permeable fractures, in order for large volumes of hydrocarbons to move.

trap

if oil or gas escapes from the reservoir rock and ultimately reaches the Earth's surface, where it leaks away at an 'oil seep', there will be none left underground to pump. Thus, for an oil reserve to exist, oil and gas must be trapped underground in the reservoir rock, by means of a geologic configuration called a ___. A field contains one or more of these. There are four types: anticline, fault, salt-dome, and stratigraphic.

seal rock

a component to an oil/gas trap; a relatively impermeable rock such as shale, salt, or unfractured limestone, must lie above the reservoir rock and stop the hydrocarbons from rising further. Also, the seal and reservoir rock bodies must be arranged in a geometry that collects the hydrocarbons in a restricted area.

seismic-reflection profile

geologists, in their search for oil deposits, look for a region containing appropriate sedimentary rocks. Then they compile a geologic map of the area, showing the distribution of rock units. From this information, it may be possible to construct a preliminary cross section depicting the geometry of the sedimentary layers underground as they would appear on an imaginary vertical slice through the Earth. To construct this profile, a special vibrating truck or a dynamite explosion sends seismic waves into the ground, with such information the computer constructs an image of the configuration of underground rock layers.

rotary drills

once the decision has been made by a geologist, drillers go to work. Using ___ ___, they grind a hole down through rock. This type of drill consists of a rotating pipe tipped by a bit, a bulb of metal studded with industrial diamond or metal prongs. As the bit rotates, it scratches and gouges the rock, turning it into powder and chips.

derricks

drillers use these towers to hoist heavy drilling pipes. To drill in an offshore oil reserve, one that occurs in strata of the continental shelf, the derrick must be constructed on an offshore-drilling facility. These offshore drilling facilities can be more than 100 stories from the base to top. In shallower water, facilities anchor on the sea floor, but in deeper water, they float on huge submerged pontoons. Drill holes can be aimed in any direction, so drillers can reach many traps from the same facility.

pump

on completion of a hole, workers remove the drilling rig and set this up. Some resemble a bird pecking for grain, moving up and down to pull up oil that has seeped into the drill hole. Simple pumping gets only about 30% of the oil in a reservoir rock out of the ground. Thus, oil companies use secondary recovery techniques to coax out up to 50% more oil - creating artificial fractures or sourcing steam into the rock.

oil consumption

the U.S. is the largest consumer of oil (at a rate of 7 million barrels per day; 25% of the world's oil consumption), but lost its position as the largest producer in the 1970s. Oil reserves in the U.S. now account for only about 4% of the world total. Thus, today the United States must import more than half of the oil it uses.

distillation column

once extracted directly from the ground, "crude oil" flows first into storage tanks and then into a pipeline or tanker, which transports it to a refinery. At a refinery, workers distill crude oil into several separate components by heating it gently in a vertical pipe called a ___ ___. Lighter molecules rise to the top of the column. Chemical factories buy the largest molecules left at the bottom and transform them into plastics.

tar sand (or oil sand)

very viscous oil reserves (such as those in Alberta and Venezuela) consisting of tarlike "heavy oil". Known as bitumen, this oil has the consistency of molasses, and thus cannot be pumped directly from the ground. Sand or sandstone containing such high concentrations of bitumen is known as ___ ___.

biodegradation

the hydrocarbon system that leads to the generation of tar sands begins with the production and burial of a source rock in a large sedimentary basin. When subjected to temperatures of the oil window, the source rock yields oil and gas, which migrate into sandstone layers and then up the dip of tilted layers to the edge of the basin, where they become caught in stratigraphic traps. Over time, microbes attacked the oil reserve underground, digested lighter, smaller hydrocarbon molecules, and left behind only the larger molecules, whose presence makes the remaining oil so viscous. Geologists refer to such a transformation process as..

oil shale

vast reserves of organic-rich shale have not been subjected to temperatures of the oil window, or if they were, they did not stay within the oil window long enough to complete the transformation to oil, and thus still contain a high proportion of kerogen. Shale that contains at least 15-30% kerogen is called __ ___. It's not the same as coal, because the organic matter within exists in the form of hydrocarbon molecules, not as elemental carbon. It takes about 40% of the energy yielded by a volume of this to produce the oil.

natural gas

consists of volatile short-chain hydrocarbons, including: methane, ethane, propane, and butane. It occurs in the pores of reservoir rock above oil, because it "floats" over the oil. Where temperatures in the subsurface are so high that oil molecules break apart to form gas, gas-only fields develop. Burns more cleanly than oil (burning gas only produces primarily carbon dioxide and water)

gas hydrate

a chemical compound consisting of a methane molecule surrounded by a cage-like arrangement of water molecules. An accumulation of this produces a whitish solid that resembles ordinary water ice. Forms when anaerobic bacteria (bacteria living in the absence of oxygen) eat organic matter such as dead plankton that have been incorporated into the sea floor. Produce methane as a byproduct, and the methane bubbles into the cold seawater that fills pore spaces in sediments. Under pressures found at water depths greater than 300 m, the methane dissolves in water and produces these molecules.

coal

a black, brittle, sedimentary rock that burns, consists of elemental carbon mixed with minor amounts of organic chemicals, quartz, and clay. This and its counterpart, oil, do not have the same composition or origin. In contrast to oil, this forms from plant material (wood, stems, leaves) that once grew in coal swamps, regions that resembled the wetland and rain forests of modern tropical to semitropical coastal areas.

most extensive deposits of coal

occurred during the Carboniferous age. The abundance of Carboniferous coal reflects (1) the past position of the continents, warm climate in which vegetation flourished; (2) the height of sea level, at this time shallow seas bordered by coal swamps covered vest parts of continental interiors.

formation of coal

how the remains of plants transform into coal; the vegetation of an ancient swamp must fall and be buried in an oxygen-poor environment, so that it can be incorporated in a sedimentary sequence without first reacting with oxygen or being eaten. Compaction and partial decay of the vegetation transforms it into peat, which contains about 50% carbon, where deposits formed from moss and grasses in bogs during the last several thousand years.

transform peat into coal

transformation process; peat must be buried deeply (4-10 km) by sediment. Such deep burial can happen where the surface of the continent gradually sinks, creating a depression, or sedimentary basin, that can collect sediment. Sea level changes, transgression and regression, numerous peat layers in the sediment accumulate. Heat and pressure applied, chemical reactions occur destroying plant fibers and releasing hydrogen, nitrogen, and sulfur gases, once the proportion of carbon in the residue exceeds 70%, we have coal. With further burial and higher temperatures, chemical reactions remove additional hydrogen, nitrogen, and sulfur, yielding progressively higher concentrations of carbon.

coal transformation sequence

with increasing burial, peat transforms into a soft dark-brown coal called 'lignite'. At higher temperatures (about 100-200 C), lignite in turn, becomes dull, black 'bituminous coal'. At even higher temperatures (about 200-300 C), bituminous coal is transformed into shiny, black 'anthracite coal'. Formation requires high temperatures that develop only on the borders of mountain belts, so sediment ends up at depths of 8-10 km, where temperatures reach 300 C.

coal rank

as the carbon content of coal increases, we say the __ __ increases. The progressive transformation of peat to anthracite coal, which occurs as the coal layer is buried more deeply and becomes warmer, reflects the completeness of chemical reactions that remove water, hydrogen, nitrogen, and sulfur from the organic chemicals of the peat and leave behind carbon.

coal reserves

because the vegetation that eventually becomes coal was initially deposited in a sequence of sediment, coal occurs as sedimentary beds interlayered with other sedimentary rocks. To find coal, geologists search for sequences of strata that were deposited in tropical to semitropical, shallow-marine to terrestrial (fluvial or deltaic) environments - the environments in which a swamp could exist. The sedimentary strata of continents contain huge quantities of discovered coal, or __ ___.

strip mining

if the coal seam lies within 100 m of the ground surface, this method of mining proves to be the most economical. Miners use a giant shovel called a drag line to scrape off soil and layers of sedimentary rock above the coal seam. Once the seam is exposed, it then scrapes out the coal and dumps it into trucks.

underground mining

the only way deeper coal can be obtained. Miners dig shafts down to the depth of the coal seam and then create a maze of tunnels, using huge grinding machines that chew their way int the coal. Dangers include collapses, black lung, and methane explosion risks.

coalbed methane

the natural process by which coal forms underground yields large quanitities of methane, a type of natural gas. Over time, some of the gas escapes to the atmosphere, but vast amounts remain within the coal. Such ___ ___, trapped in strata too deep to be reached by mining, is a valuable energy resource that has become a target for exploration around the world. Obtaining this methane involves drilling instead of mining.

coal gasification

coal can be transformed into various gases, as well as solid byproducts, before burning, and the gases burn quite cleanly. The process of producing clean-burning gases from solid coal is called __ _____. Pulverized coal is contained, then a mixture of steam and oxygen passes through the coal at high pressure. The coal heats up to higher temperatures, chemical reactions break down the carbon molecules in coal and produce hydrogen. Solid ash, as well as sulfur and mercury, concentrate at the bottom of the container - the contaminants do not go up into the atmosphere.

nuclear fission

the breaking of the nuclear bonds that hold protons and neutrons together in the nucleus provides the energy. Fission occurs when a neutron strikes a radioactive atom, causing it to split; splitting an atom into smaller pieces. During this process, a tiny fraction of the matter composing the original atom is transformed into a large amount of thermal and electromagnetic energy. Just one gram of nuclear-reactor fuel yields as much energy as 2.7 barrels of oil.

nuclear reactor

first built to produce electricity during the 1950s. This is the heart of the nuclear plant, commonly lies within a dome-shaped shell (containment building) made of reinforced concrete. The reactor contains nuclear fuel packed into metal tubes called fuel rods. The pipe within the plant carry steam, produced from water near the heat-generating nuclear fuel, into a turbine where the rotation drives a dynamo that generates electricity.

chain reaction

the neutrons released during nuclear fission of one atom strike other atoms, thereby triggering more fission in a self-perpetuating process called a ___ ___.

geology of Uranium

U-235, an isotope of uranium containing 143 neutrons, is the most common fuel for conventional nuclear power plants. U-235 only accounts for about 0.7% of naturally occurring Uranium, thus to make a fuel suitable for use in a power plant, the U-235 concentration in a mass of natural uranium must be increased by a factor of 2 or 3, an expensive process called enrichment.

Uranium formation

uranium is concentrated by hot water percolating through a granitic pluton after intrusion dissolves the uranium and precipitates it, along with other elements, in cracks. Uranium from veins typically occurs in the mineral pitchblende (UO2). The world's richest uranium deposits occur in ancient stream-bed deposits. Prospectors use a Geiger counter to find uranium, an instrument that detects radioactivity.

meltdown

to order to maintain nuclear power plant safety, operators must constantly cool the nuclear fuel with circulating water, and the rate of nuclear fission must be regulated by the insertion of boron-steel control rods, which absorb neutrons and thus decrease the number of collision between neutrons and radioactive atoms. If left uncontrolled, so many neutrons begin to dash about in the fuel rods that the rate of fission becomes too fast and the fuel rods become too hot, in which case they melt and cause a..

nuclear waste

the radioactive material produced in a nuclear plant, includes spent fuel, which contains radioactive daughter products as well as water and equipment that may have been in contact with radioactive materials. Radioactive elements emit gamma rays and X-rays that can damage living organisms and cause cancer. Waste can sometimes remain dangerous for thousands of years or more; high-level waste contains greater than 1 million times the safe level of radioactivity, intermediate-level contains between 1 million and 1 thousand, and low-level waste contains less than 1 thousand times the safe level.

disposing of nuclear waste

nuclear waste cannot simply be stashed in a warehouse or buried in a town landfill, groundwater passing through the dump site might transport radioactive elements into municipal water supplies or nearby lakes/streams. Ideally, waste should be sealed in containers that will last for thousands of years, geoscientists have suggested these possibilities: underground mountain tunnels, interiors of impermeable salt domes, landfills surrounded by absorbent clay, landfills in regions where groundwater composition can react with radioactive atoms to form non movable minerals, the deep ocean floor where it can be subducted.

geothermal energy

refers to heat and electricity produced by using the internal heat of the Earth, exists because the Earth grows progressively hotter with depth. Produces energy in two ways: can simply pump hot groundwater out of the ground and run it through pipes to heat homes, elsewhere the groundwater is so hot that when it rises to the Earth's surface and decompresses, it turns to steam - which is used to drive turbines and generate electricity.

hydroelectric power

as water flows downslope, its potential energy converts into kinetic energy, the water flow drives turbines which drives generators that produce electricity. In order to increase the rate and volume of water flow in these dams, engineers build dams to create reservoirs that retain water and raise it to a higher elevation - the water flows through pipes down to turbines at the foot of the dam.

wind power

wind farms have been established around to world to generate electricity. The electricity is clean, but wind production requires the construction of large, noisy towers.

solar power

this energy is abundant but diffuse - on the sunniest of days, each square meter of the Earth surface receives about 1,000 watts of energy. How can this energy be concentrated sufficiently to produce heat and electricity? At present energy consumers have two options: solar collectors and photovoltaic cells.

solar collector

option for using solar power; a device that collects energy to produce heat, one class of these includes mirrors and lenses that focus light striking a broad area into a smaller area. Another class of collector consists of a black surface placed beneath a glass plate, the surface absorbs light passing through the plate and heats up. When a consumer runs water between the glass and the black surface, the water heats up and can then be stored in an insulated tank.

photovoltaic cells

option for using solar power; the use of these solar cells allows light energy to convect directly into electricity. Most PV cells consist of two wafers of silicon pressed together, silicon is a semiconductor meaning that it can conduct electricity only when doped with impurities; "doping" means that manufacturers intentionally add atoms other than silicon to the wafer. The two wafers are doped with arsenic and boron, when light strikes the cell, the electrons gain energy to cross the boundary and an electrical current flows.

biofuels

in recent years, farmers have begun to produce rapidly growing crops specifically for the purpose of creating biomass for fuel production. The resulting liquids are ___.

production of ethanol

the most commonly used biomass fuel; produced from the fermentation of sugar derived from corn or sugar cane. Production includes three steps: (1) grain is grinded into a fine powder, mixed with water, and cooked to produce a mash of starch; (2) farmers add an enzyme to the mash, which converts the mash into sugar; (3) they mix in yeast and allow it to ferment; (4) the fermented mash is then distilled to concentrate the ___.

fuel cells

in a __ __, chemical reactions produce electricity directly. In a hydrogen fuel cell, hydrogen gas flows through a tube across an anode (a strip of platinum) that has been placed in a water solution containing an electrolyte. At the same time, a stream of oxygen gas flows onto a separate platinum cathode that also has been placed into the solution, a wire connects the anode and the cathode to create an electrical circuit. In this configuration, hydrogen reacts with oxygen to produce water, about 40-80% of the chemical energy released by this reaction produces electricity, the rest becomes heat.

Oil Age

Oil is finite and non-renewable so there will be an end to this age. It takes millions of years for oil to generate and humans are using it all in mere centuries.

acid rain

rain containing acids that form in the atmosphere when industrial gas emissions (especially sulfur dioxide and nitrogen oxides) combine with water. A dilute solution of sulfuric acid produced when sulfur-bearing minerals such as pyrite in mines can react with rainwater. The runoff enters streams and kills fish and plants.

MINERAL RESOURCES

minerals extracted from the Earth's upper crust that are of use to civilization. Without these resources, industrialized societies could not function. Two categories: metallic (rocks containing gold, copper, aluminum, iron) and nonmetallic (building stone, gravel, sand, gypsum, phosphate, salt).

metals

opaque, shiny smoot solids that can conduct electricity and can be bent, drawn into wire, or hammered into thin sheets. They look and behave quite differently from wood, plastic, meat, or rock. Unlike other substances, the atoms that make up metals are held together by metallic bonds, meaning that the outer electrons flow from atom to atom fairly easily.

native metals

certain metals - namely, copper, silver, gold, and mercury - can occur in rock as ___ ___. Consist of only metal atoms, and thus look and behave like metal.

smelting

most of the metal atoms we use today originated as ions bonded to nonmetallic elements in a great variety of minerals that themselves look nothing like metal. Only because of the chance discovery by some prehistoric genius that certain rocks, when heated to high temperatures in fire, a process called ___, decompose to yield metal plus a nonmetallic residue called slag do we now have the ability to produce sufficient metal for the needs of industrialized society.

alloy

a compound containing two or more metals

copper

of the three principle metals used today, this began to be used first, because copper smelting from sulfide minerals is relatively easy. Can be mixed with tin to produce bronze, an alloy whose strength exceeds that of either metal alone, and warriors came to rely on bronze for their swords.

iron

of the three principle metals, this one proved superior to copper or bronze for many purposes because of its strength, hardness, and abundance. Has a very high melting temperature that can be difficult to reach, in addition, the metal generally occurs in ___-oxide minerals and liberation of iron metal from oxide minerals requires a chemical reaction, not just simple heating.

aluminum

one of the three principle metals used; is abundant in rocks of the crust and, in many ways, is preferable to iron because it weighs less. But is does not occur in native form, and the extraction of ____ from minerals requires complex methods.

precious metals

classification of metal; gold, silver, platinum

base metals

classification of metal; copper, lead, zinc, and tin

ore

to obtain the metals needed for industrialized society, we mine __, rocks containing a concentrated accumulation of native metals or __ minerals.

ore minerals (or economic minerals)

minerals that contain metal in high concentrations and in a form that can be easily extracted. Galena, for example, is about 50% lead, so we consider it to be an __ ___ of lead. We obtain most of our iron from the oxide minerals, hematite and magnetite.

grade (of the ore)

to be an ore, a rock must not only contain ore minerals, it must also have a sufficient amount to make it worth mining. Iron constitutes about 6.2% of the continental crust's weight, whereas it makes up about 30 to 60% of iron ore. The concentration of a useful metal in an ore determines the ___ of the ore - the higher the concentration, the higher this is.

ore deposit

an economically significant occurrence of ore. The various kinds of __ ___ differ from each other in terms of which ore minerals they contain and which kind of rock body they occur in.

magmatic deposit

when magma cools, sulfide ore minerals crystallize early and then, because sulfides tend to be dense, sink to the bottom of the magma chamber, where they accumulate; this accumulation is a ____ ____.

massive-sulfide deposit

when the magma freezes solid within a magmatic deposit, the resulting igneous body may contain a solid mass of sulfide minerals at its base. Because of their composition, we consider these masses to be a type of..

hydrothermal deposit

hydrothermal activity dissolves metal ions, when a solution enters a region of lower pressure, lower temperature, different acidity, and/or different availability of oxygen, the metals come out of solution and form ore minerals that precipitate in fractures and pores, creating a ____ ___. Such deposits may form within an igneous intrusion or in surrounding country rock.

disseminated vs. vein (hydrothermal deposits)

from the process of a hydrothermal deposit, if the resulting ore minerals disperse through the intrusion, we call the deposit a ___ deposit. But if they precipitate to fill cracks in preexisting rock, we call the deposit a __ deposit.

secondary-enrichment deposits

a new ore deposit formed from metals that were dissolved and carried away from a preexisting ore deposit. Some of these deposits contain spectacularly beautiful copper-bearing carbonate minerals, such as azurite and malachite.

banded-iron formations

iron-rich sedimentary layers, because after lithification they consist of alternating beds of gray iron oxide (magnetite or hematite) and red beds of jasper (iron-rich chert). Microbes may have participated in the precipitation process.

manganese nodules

the chemistry of seawater in some parts of the ocean today leads to the deposition of managese-oxide minerals on the sea-floor. These minerals grow into lumpy accumulations known as ____ ___.

residual mineral deposits

in rainy, tropical environments, the residuum left behind in soils after leaching includes concentrations of iron or aluminum. Locally, these metals become so concentrated that the soil itself becomes an ore deposit. For example, most of the aluminum ore mined today comes from bauxite, a ___ ___ ___ created by the extreme leaching of rocks (granite) containing aluminum-bearing minerals.

placer deposit

concentrations of metal grains in stream sediments are a type of ___ ___. The heavy metal grains in a stream accumulate in sand or gravel bars, for the moving water carries away lighter mineral grains but can't move the metal grains so easily.

ore formation

ores from by: settling from melt, precipitating from hot water, deposition from currents, alteration by groundwater, and extreme weathering. The distribution of ores can be explained by plate tectonics, they occur along boundaries.

open-pit mine

miners use giant earth moving equipment to dig a huge pit and remove ore deposits. Workers then separate ore minerals from other minerals and send the concentrate to a processing plant, where it undergoes smelting or treatment with acidic solutions to separate metal atoms from other atoms. Eventually, workers melt the metal and then pour it into molds to make ingots for transport to a manufacturing facility.

underground mine

mine below the surface of the Earth; , best mining technique for deeper deposits in horizontal layers, more than about 100 meters below.

dimension stone

intact slabs and blocks of rock (such as granite or marble); sedimentary, metamorphic and igneous rocks that can be cut in different sizes. Used for decorative rock for the face of buildings, floors and roof tops.

mortar vs. concrete

__ refers to the substance that holds bricks or stone blocks together, whereas __ refers to the substance that workers shape into roads or walls by spreading it out into a layer or by pouring it into form. The cement in either starts out as a powder composed of lime, quartz, aluminum oxide, and iron oxide.

Portland cement

since natural limestone with the exact composition of cement is relatively rare, most cement used today is ___ ___, made by mixing limestone, sandstone, and shale in just the correct proportions to provide the correct chemical makeup.

crushed stone

any variety of coherent rock (limestone, quartzite, granite, gneiss); forms the substrate of highways and railroads and is the raw material for manufacturing cement, concrete, and asphalt. In these quarries, operators use high explosives to break up bedrock into rubble that they then transport by truck to a jaw crusher, which reduces the rubble to usable-size fractions.

limestone

sedimentary rock made of calcite; used for gravel or cement

siltstone

beds of sedimentary rock; used to make flagstone

granite

coarse igneous rock; used for dimension stone

marble

metamorphosed limestone; used for dimension stone

slate

metamorphosed shale; used for roofing shingles

gypsum

a sulfate salt precipitated from saltwater; used for wallboard

phosphate

from the mineral apatite; used for fertilizer

pumice

frothy volcanic rock; used to decorate gardens and paths

clay

very fine mica-like material in sediment; used to make bricks or pottery

sand

from sandstone, beaches, or riverbeds; quartz sand is used for construction and for making glass

salt

from the mineral halite, formed by evaporating saltwater; used for food, melting ice on roads

sulfur

occurs either as native sulfur, typically above salt domes, or in sulfide minerals; used for fertilizer and chemicals

reserves

mineral resources, like oil and coal, are nonrenewable resources. Once mined, an ore deposit or a limestone hill disappears forever, natural geologic processes do not happen fast enough to replace the deposits as quickly as we use them. Geologists have calculated ___ (measured quantities of a commodity) for various mineral deposits just as they have for oil. Based on current definitions of these and rates of consumption, supplies of some metals may run out in only decades to centuries.

strategic metals

include manganese, platinum, chromium, and cobalt - metals alloyed with iron to make the special-purpose steels needed in the aerospace industry. Principal reserves of these metals lie in the crust of countries that have not always practiced open trade with the U.S., as a defense precaution the U.S. stockpiles these metals.

MASS MOVEMENT

geologists refer to the gravitationally caused downslope transport of rock, regolith (soil, sediment, and debris), snow, ice as __ ___, or mass wasting. They are the most costly natural hazard, also they play a critical role in the rock cycle, for it's the first step in the transportation of sediment. It's the most rapid means of modifying the shapes of slopes.

natural hazard

like earthquakes, volcanic eruptions, storms, and floods, mass movements are a type of ___ ___, meaning a natural feature of the environment that can cause damage to living organisms and to buildings.

4 factors of mass movement

geologists distingiush among different types of mass movement on the basis of these factors: the type of material involved (rock, regolith, or snow or ice), the velocity of the movement (fast, intermediate, or slow), the character of the moving mass (chaotic cloud, slurry, or coherent body), and the environment in which the movement takes place (subaerial or submarine).

creep

during the spring thaw, water becomes liquid again, and gravity makes the particles sink vertically and thus migrate downslope lightly. This gradual downslope movement of regolith is called ___. Happens over a period of years it causes trees, fences, gravestones, walls, and foundations built on a hillside to tilt downslope.

solifluction

Slow, downslope flow of water-saturated materials common to permafrost or tundra (cold, treeless ragions) areas.

rock glaciers

another type of slow mass movement in cold regions takes place in __ ___, which consist of a mixture of rock fragments and ice, with the rock fragments making up the major proportion. These develop where the volume of debris falling into a valley equals or exceeds the volume of glacial ice forming from snow.

failure surface

during slumping, a mass of regolith detaches and slips semicoherently downslope. We call the moving mass itself a slump, and the surface on which it slips a ___ ___. On average, the sea cliffs of southern California retreat (move inland) by up to a few meters a year because of slumping.

head scarp

the distinct, curving step at the upslope edge of a slump, where the regolith detached, is called a __ __. Immediately below this, the land surface sinks below its previous elevation. Farther downslope, at the end of the slump, the ground elevation rises as the slump mass rides up and over the preexisting land surface. The end (the toe) may break into a series of slices that form curving ridges at the ground surface.

mudflow

in areas such as hill-slope communities of Rio, where neither vegetation nor drainage systems protect the ground from rainfall, water mixes with regolith to create a slurry that moves downslope. If the slurry consists of just mud, it's a ___, but if the mud is mixed with larger rock fragments, it's a debris flow.

lahars

particularly devastating mudflows spill down the river valleys bordering volcanoes. These mudflows, known as ___, consist of a mixture of volcanic ash from a currently erupting or previously erupted pyroclastic cloud, and water from the snow and ice that melts in a volcano's heat or from heavy rains.

landslide

geologists refer to the sudden movement of rock and debris down a nonvertical slope as a ___. If the mass consists only of rock, it may also be called a rock slide, and if it consists mostly of regolith, it may also be called a debris slide. Once one has take place, it leaves a scar on the slope and forms a debris pile at the base of the slope.

landslide occurrence

slides happen when bedrock and/or regolith detaches from a slope and shoots downhill on failure surface roughly parallel to the slope surface. Thus, landslides generally occur where a weak layer of rock or sediment at depth below the ground parallels the land surface. Slides may move at speeds up to 300 km per hour; they are particularly fast when a cushion of air gets trapped beneath, so there is virtually no friction between the slide and its substrate, and the mass moves like a hovercraft.

avalanche

turbulent clouds of debris mixed with air that rush down steep hill slopes at high velocity. If the debris consists of snow, like the Austrian one, it's a snow ____. If it consists of rock and dust, it's a debris ____. The moving-air debris mass is denser than clear air, thus it hugs the ground and acts like an extremely strong and viscous wind that can knock down and blow away anything in its path.

rockfalls

these happen when large blocks of rock break loose from a cliff face, or steep slope, along a joint and start tumbling.

debris falls

Type of slope failure that occurs when a mixture of soil, regolith, and rocks becomes dislodged and falls down the slope.

talus

a sloping mass of loose rocks at the base of a cliff; friction and collision with other rocks may bring some blocks to a halt before they reach the bottom of the slope.

submarine slumps

form of submarine mass movement; semicoherent blocks (olistostromes) slip downslope on weak mud detachments. In some cases, the layers constituting the blocks become contorted as they move, like a tablecloth that has slid off a table.

submarine debris flows

type of submarine mass movement; the moving mass breaks apart to form a slurry containing larger clasts (pebbles to boulders) suspended in a mud matrix.

turbidity currents

type of submarine mass movement; sediment disperses in water to create a turbulent cloud of suspended sediment that avalanches downslope. As this current slows, sediment settles out in sequence from coarse to fine, creating graded beds.

cause of mass movements

in order for these movements to take place, the stage must be set by the following phenomena; fracturing and weathering, which weaken materials at Earth's surface so that they cannot hold up against the pull of gravity; and the development of relief, which provides slopes down which masses move. The velocity of these movements depends on the steepness of the slope and the water or air content of the mass.

angle of repose

what causes resistance force? Chemical bonds in mineral crystals, cement, and the interlocking of crystals hold intact rock in place, friction holds an unattached block in place, electrical charges and friction hold dry regolith in place, and surface tension holds slightly wet regolith in place. Because of resistance force, granular debris tends to pile up and create the steepest slope it can without collapsing. The angle of this slope is called the __ _ ___, and for most dry, unconsolidated materials (such as dry sand) it typically has a value between 30 and 37 degrees.

slope failure surfaces

in many locations, the resistance force is less than might be expected because a weak surface exists at some depth below ground level. This weak surface separates unstable rock and debris above from the substrate below. These include: wet clay layers, wet unconsolidated sand layers, surface-parallel joints (exfoliation joints), weak bedding planes (shale and evaporite beds), and metamorphic foliation planes.

quick clay

groundshaking produces a unique effect in certain types of clay. This clay consists of damp clay flakes, behaves like a solid when still, for surface tension holds water-coated flakes together. But shaking separates the flakes from one another and suspends them in the water, thereby transforming the clay into a slurry that flows like a fluid.

liquefaction

The process by which an earthquake's violent movement suddenly turns loose soil into liquid mud.

dip slope

when bedding on a mountain parallels the face of the mountain itself.

undercutting

in some cases, excavation results in the formation of an overhang. When such ____ has occurred, rock making up the overhang eventually breaks away from the slope and falls. Overhangs commonly develop above a weak horizontal layer that erodes back preferentially, or along seacoasts and rivers where the water cuts into a fairly strong slope.

landslide-potential maps

identify slide prone areas and potentially unstable slopes. The factors considered include: slope steepness, strength of substrate, degree of water saturation; orientation of bedding, joints, or foliation relative to the slope; nature of vegetation cover; potential for heavy rains; potential for undercutting to occur; and likelihood of earthquakes in an area.

riprap

loose boulders or concrete

preventing mass movements

in areas where hazard exists, people can take certain steps to remedy the problem and stabilize the slope: re-vegetation, regrading, reducing subsurface water, preventing undercutting, constructing safety structures, and controlling blasting of unstable slopes.

RUNNING WATER

water that flows down the surface of sloping land in response to the pull of gravity.

stream

geologists use this term for any channelized body of running water, meaning water that flows along a channel, an elongate depression or trough.

flood

generally, a stream stays within the confines of its channel , but when the supply of water entering a stream exceeds the channel's capacity, water spills out and covers the surrounding land, thereby causing a ___, such as the one that washed away Johnstown.

runoff

the portion of meteoric water that eventually ends up in streams, includes water that has passed through a variety of surface and subsurface reservoirs in the hydrologic cycle.

sky

type of runoff pathway; some water falls directly from the __ onto the surface of a stream. Generally, this water makes only a small contribution to a stream's volume.

standing body

type of runoff pathway; in places where the ground surface is flat or forms a depression, water accumulates in a ___ ___ (puddle, swamp, pond, lake). When the water level in the standing body becomes higher than the lowest point along the body's bank, an outlet forms, through which water spills into a stream.

sheetwash

type of runoff pathway; on slopes, water can move as ____ - a thin film up to a few millimeters thick - down the ground surface to a lower elevation. This water either enters a stream directly or first enters a standing body and later flows through an outlet into a stream.

subsurface water

type of runoff pathway; where the ground surface is permeable, water can infiltrate down and become ____ ___. Includes soil, moisture, vadose-zone water (water that partially fills cracks and pores in rock or regolith below the soil but above the water table), and groundwater (water that completely fills cracks and pores in the region below the water table)

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