Chapter 16 Geology and Nonrenewable Mineral Resources

What is the Earth’s Structure? Core: Earth’s innermost zone; very hot; solid inner part surrounded by a liquid core Mantle: surrounds the core; mostly solid rock; outermost part is very hot, partly melted rock (like flowing plastic) Crust: outermost and thinnest zone; consists of the continental crust (underlies continents) and the oceanic crust (underlines oceans)

Mantle Core Crust Low-velocity zone Solid Outer core (liquid) Inner core (solid ) 35 km (21 mi.) avg., 1,200˚C 2,900km (1,800 mi.) 3,700˚C 5,200 km (3,100 mi.), 4,300˚C 10 to 65km 100 km 200 km 100 km (60 mi.) 200 km (120 mi.)

Oceanic crust (lithosphere) Abyssal floor Oceanic ridge Trench Volcanoes Mantle (lithosphere ) Mantle (asthenosphere ) Abyssal plain Continental crust (lithosphere) Mantle (lithosphere) Continental slope Continental shelf Abyssal plain Abyssal floor Earth’s Crust and Mantle

Movement of Heat within the Earth Internal Processes: originate from the Earth’s interior Decay of radioactive elements in the crust adds to heat within the mantle Two types of heat movement happen inside the mantle: 1.Convection Cells: large volumes of heated rock move (like pot of boiling water) 2.Mantle Plumes: mantle rock flows upward in a column (like smoke from a chimney)

What are Tectonic Plates? Convection cells and mantle plumes both move upward as heated material is displaced by cooler, sinking material These flows of energy cause movement of “tectonic plates” Plates are about 60 miles thick Composed of continental and oceanic crust, and the outermost part of the mantle

Tectonic plate Collision between two continents Oceanic tectonic plate Spreading center Oceanic tectonic plate Ocean trench Plate movement Continental crust Oceanic crust Continental crust Mantle Inner core Hot outer core Two plates move towards each other. Hot material rising through the mantle Material cools as it reaches the outer mantle Cold dense material falls back through mantle

More about Plate Tectonics Tectonic plates move constantly, like large pieces of ice on lake surface Move about the rate of fingernails growing Widely accepted theory in the 60s. Throughout history, continents have drifted apart and joined together as plates move back and forth across Earth’s surface

More about Plate Tectonics Produces mountain and ocean ridges Volcanoes and earthquakes are found at plate boundaries Allows us to trace how species migrated from one area to another

VolcanoesEarthquakes Earthquake and Volcano Sites

Boundaries Between Earth’s Plates Divergent Plate Boundaries: plates move in opposite directions Convergent Plate Boundaries: plates are pushed together by internal forces; forms a trench Transform Faults: occur where plates slide past one another; most are on the ocean floor

Between Earth’s Plates External Processes: geological changes based on energy from the sun or gravity Erosion: material is dissolved, loosened, or worn away from one part of the Earth’s surface and THEN deposited in other places Wind can cause erosion as soil is blown from one area to another Human activities accelerate erosion

Continued… Weathering: process that loosens material that can be eroded Two Types of Weathering: 1.Mechanical Weathering: large rock mass is broken into smaller fragments; Frost Wedging (water collects in pores of rocks, expands, and splits rock) 2.Chemical Weathering: chemical reactions decompose a mass of rock

Dunes Lagoon Spits Stream Glacier Lake Tidal flat Barrier islands Shallow marine environment Volcanic island Coral reef Abyssal plain Continental shelf Continental slope Continental rise Delta Dunes Beach Shallow marine environment

Minerals and Rocks Earth’s crust is composed of minerals and rocks Mineral: element or inorganic compound that occurs naturally and is solid (gold, silver, salt, quartz) Rock: any material that makes up a large, natural, continuous part of the Earth’s crust; most rocks consists of two or more minerals

Three Major Types of Rocks 1.Igneous Rock: formed below or on Earth’s surface when magma (molten rock) wells up, cools, and hardens into rock (granite, lava rock) 2.Sedimentary Rock: formed from sediment when rocks are eroded, transported to another place, and deposited in water (sandstone) 3.Metamorphic Rock: rock is subjected to high temperature, high pressure, or chemically active fluids (coal, slate, marble)

Rock Cycle Rocks are constantly exposed to changing conditions Interaction of processes that change rocks from one type to another is called the Rock Cycle Slowest of all Earth’s cycles; recycles material over millions of years

Igneous Rock Granite, pumice, basalt Metamorphic Rock Slate, marble, Magma (molten rock) Cooling Heat, pressure Melting Heat, pressure, stress Sedimentary Rock sandstone, limestone DepositionTransportation Erosion Weathering EXTERNAL PROCESSES INTERNAL PROCESSES ROCK CYCLE

Earthquakes Stress in the Earth’s crust can cause solid rock to deform until it fractures and shifts along the fracture (fault) Abrupt movement of an existing fault causes an earthquake When fracture happens, energy is released as shock waves

Measuring Earthquakes Magnitude: severity of an earthquake Measure amount of energy released in an earthquake Categories: insignificant, minor, damaging, destructive, major, great Each level is 10x greater than the previous

How Can We Reduce Earthquake Hazards? Examine historical records and make measurements to locate active fault zones Make maps to show high-risk areas Establish building codes for high-risk areas Try to predict where and when earthquakes will occur

Volcanoes Occurs where magma (molten rock) reaches the Earth’s surface through a crack Volcanic activity can release: debris (hot lava rock or ash), liquid lava, gases These gases may become concentrated in the atmosphere and become concentrated into sulfuric acid

extinct volcanoes magma reservoir central vent lithosphere Upwelling magma Volcano

Aftermath of Volcanoes Between 1985 and 1999: 561,000 people died from natural disasters; about 30% of these were from earthquakes and volcanic eruptions Benefits: scenery, lakes (Crater Lake in Oregon), fertile soil from weathering lava

How Can We Reduce Volcano Hazards? Land-use planning Better prediction of volcanic eruptions Evacuation plans