ENSP101Chapter 14 – Geology and Earth Resources14.1 Earth Processes Shape Our Resources- Core – the dense, intensely hot mass of molten metal, mostly iron and nickel, thousands of km’s in diameter at the earth’s enter- Mantle – a hot, pliable layer of rock that surrounds the earth’s core and underlies the cool, outer crust- Crust – the cool, lightweight, outermost layer of the earth’s surface that floats on the soft, pliable underlying layers- Tectonic plates –huge blocks of the earth’s crust that slide around slowly, pulling apart to open new ocean basins or crashing ponderously into each other to create new, larger landmasseso These plates slide slowly across the earth’s surface like wind-driven ice sheets on water, in some places breaking up into smaller pieces, in other places crashing ponderously into each other to create new, larger landmasseso Ocean basins form where continents crack and pull aparto Magma – molten rock from deep in the earth’s interior; called lava when it spews from volcanic vents Mid-ocean ridges – mountain ranges on the ocean floor created where molten magma is forced up through cracks in the planet’s crust Creating the largest mountain range in the world, these ridges wind around the earth for 74,000 km Although concealed from our view, this jagged range boasts higher peaks, deeper canyons, and sheerer cliffs than any continental mountainso Earthquakes are caused by grinding and jerking as plates slide past each othero When an oceanic plate collides with a continental landmass, the continental plate usually rides up over the seafloor, while the oceanic plate is subducted, or pushed down into the mantle, where it melts and rises back to the surface as magmao Deep ocean trenches mark these subduction zones, and volcanoes form where the magma erupts through vents and fissures in the overlying crusto Over millions of years, continents can drift long distanceso The redistribution of continents has profound effects on the earth’s climate and mayhelp explain the periodic mass extinctions of organisms marking the divisions between many major geologic periods14.2 Rocks and Minerals- Mineral – a naturally occurring, inorganic, crystalline solid with definite chemical composition and characteristic physical propertieso The 2 fundamental characteristics of a mineral that distinguish it from all other minerals are its chemical composition and its crystal structure No 2 minerals are identical in both respects- Rock – a solid, cohesive, aggregate of one or more mineralso Within the rock, individual mineral crystals (or grain) are mixed together and held firmly in a solid masso The grains may be large or small, depending on how the rock was formed, but each grain retains its own unique mineral qualitieso Rock cycle - the process whereby rocks are broken down by chemical and physical forces; sediments are moved by wind, water, and gravity, sedimented and reformed into rock, and then crushed, folded, melted, and re-crystallized into new formso There are 3 major rock classifications: igneous, sedimentary, and metamorphic Igneous:- Igneous rocks – crystalline minerals solidified from molten magma from deep in the earth’s interior; balat, rhyolite, andesite, lava, and granite are examples- The most common rock-type in the earth’s crust is solidified form magma, welling up from the earth’s interior Metaphoric:- Preexisting rocks can be modified by heat, pressure, and chemical agents to create new forms called metamorphic rock Sedimentary:- Weathering and sedimentation wear down rocks- Most of these crystalline rocks are extremely hard and durable, but exposure to air, water, changing temperatures, and reactive chemicalagents slowly breaks them down in a process called weatheringo Mechanical weathering is the physical breakup of rocks into smaller particles without a change in chemical composition of the constituent mineralso Chemical weathering is the selective removal or alteration of specific components that leads to weakening and disintegration of rocko Among the more important chemical weathering processes are oxidation (combination of oxygen with an element to form an oxide or hydroxide mineral) and hydrolysis (hydrogen atoms from water molecules combine with other chemicals to form acids)- Sedimentation – the deposition of organic materials or minerals by chemical, physical, or biological processes- Sedimentary rock – deposited material that remains in place long enough or is covered with enough material to compact into stone; examples include shale, sandstone, breccia, and conglomerates- Sedimentary rocks are also formed from crystals that precipitate out of, or grow from a solution- Sedimentary formations often have distinctive layers that show different conditions when they were laid down14.3 Economic Geology and Mineralogy - Economic mineralogy is the study of minerals that are valuable for manufacturing and are, therefore, an important part of domestic and international commerce- Most economic minerals are metal-bearing ores- Nonmetallic economic minerals are mostly graphite, some feldspars, quartz crystals, and diamonds- Most economically valuable crustal resources exist everywhere is small amounts; the important thing is to find them concentrated in economically recoverable levels- Metals are essential to our economy- Sand and gravel production comprise by far the greatest volume and dollar value of all nonmetal mineral resources and a far greater volume than all metal oreso Sand and gravel are used mainly in brick and concrete construction, paving, as lose road filler, and for sandblastingo High-purity silica sand is our source of glass- Limestone, like sand and gravel, is mined and quarried for concrete and crushed for road rock- Evaporites (materials deposited by evaporation of chemical solutions) are mined for halite, gypsum, and potash- Sulfur deposits are mined mainly for sulfuric acid production14.4 Environmental Effects of Resource Extraction- The most obvious effect of mining is often the disturbance or removal of the land surfaceo Farther-reaching effects include air and water pollutiono Chemical and sediment-runoff pollution is a major problem in many local watershedso After use in ore processing, most water contains sulfuric acid, arsenic, heavy metals, and other contaminantso Mine runoff leaking into lakes and streams damages or destroys aquatic ecosystems- Mining can have