Geology and Nonrenewable Minerals Chapter 12
Section 12-1 What are the earth’s major geological processes and hazards?
The earth is a dynamic planet • Geology is the science devoted to the study of dynamic processes occurring on the earth’s surface and in its interior. • Three major concentric zones. • The core is the earth’s innermost zone—extremely hot, with a solid inner part encircled by a liquid core of molten or semisolid material. • Surrounding the core is a thick zone called the mantle—solid rock, but under its rigid outermost part is the asthenosphere, a zone of hot, partly melted rock that flows.
The earth is a dynamic planet • The outermost and thinnest zone of the earth is the crust. • Continental crust, which underlies the continents. • Oceanic crust, which underlies the ocean basins and makes up 71% of the earth’s crust. • The combination of the crust and the rigid outermost part of the mantle (above the asthenosphere) is called the lithosphere.
Folded mountain belt Volcanoes Abyssal plain Abyssal floor Oceanic ridge Abyssal floor Abyssal hills Craton Trench Oceanic crust (lithosphere) Continental shelf Abyssal plain Continental slope Continental rise Continental crust (lithosphere) Mantle (lithosphere) Mantle (lithosphere) Mantle (asthenosphere) Fig. 12-2, p. 277
The earth beneath your feet is moving • Convection cells or currents move large volumes of rock and heat in loops within the mantle like gigantic conveyer belts. • Flows of energy and heated material in these convection cells caused the lithosphere to break up into a dozen or so huge rigid plates, called tectonic plates. • Continents have split apart and joined as tectonic plates drifted atop the earth’s asthenosphere.
The earth beneath your feet is moving • The forces produced at these plate boundaries can cause earthquakes, erupting volcanoes and mountains to form. • Oceanic plates move apart from one another allowing magma, to flow up between them. • Much of the geologic activity at earth’s surface takes place at the boundaries between tectonic plates as they move in the resulting cracks. • Oceanic ridges may have peaks higher and canyons deeper than those found on the earth’s continents.
The earth beneath your feet is moving • When two oceanic plates collide, a trench ordinarily forms at the boundary between the two plates. • When an oceanic plate collides with a continental plate, the continental plate usually rides up over the denser oceanic plate and pushes it down into the mantle in a process called subduction. • The area where this collision and subduction takes place is called a subduction zone. • Tectonic plates can also slide and grind past one another along a fracture (fault) in the lithosphere—a type of boundary called a transform fault.
Spreading center Ocean trench Oceanic tectonic plate Oceanic tectonic plate Oceanic tectonic plate Plate movement Plate movement Oceanic crust Tectonic plate Subduction zone Oceanic crust Continental crust Continental crust Cold dense material falls back through mantle Material cools as it reaches the outer mantle Hot material rising through the mantle Mantle convection cell Mantle Two plates move towards each other. One is subducted back into the mantle on a falling convection current. Hot outer core Inner core Fig. 12-3, p. 277
EURASIAN PLATE NORTH AMERICAN PLATE ANATOLIAN PLATE CHINA SUBPLATE JUAN DE FUCA PLATE CARIBBEAN PLATE PHILIPPINE PLATE ARABIAN PLATE AFRICAN PLATE INDIA PLATE PACIFIC PLATE PACIFIC PLATE COCOS PLATE SOUTH AMERICAN PLATE NAZCA PLATE AUSTRALIAN PLATE SCOTIA PLATE ANTARCTIC PLATE Transform faults Convergent plate boundaries Divergent plate boundaries Fig. 12-4, p. 278
Internal pressure in a volcano can cause lava, ash, and gases to be ejected
Extinct volcanoes Eruption cloud Ash Acid rain Ash flow Lava flow Mud flow Central vent Landslide Magma conduit Solid lithosphere Magma reservoir Partially molten asthenosphere Upwelling magma Fig. 12-6b, p. 279
Earthquakes are geological rock-and-roll events • Forces inside the earth’s mantle and near its surface push, deform, and stress rocks. • The stress can cause the rocks to suddenly shift or break and produce a transform fault, or fracture in the earth’s crust. • When a fault forms or when there is abrupt movement on an existing fault, energy that has accumulated over time is released in the form of vibrations, called seismic waves, causing an earthquake.
Liquefaction of recent sediments causes buildings to sink Two adjoining plates move laterally along the fault line Earth movements cause flooding in low-lying areas Landslides may occur on hilly ground Shock waves Focus Epicenter Fig. 12-7, p. 280
Earthquakes are geological rock-and-roll events • The severity of an earthquake is measured by the magnitude of its seismic waves. • The magnitude is a measure of shaking caused by the earthquake, as indicated by the size of the seismic waves when they reach a seismograph. • Scientists use the Richter scale, on which each unit has amplitude 10 times greater than the next smaller unit.
Earthquakes are geological rock-and-roll events • Insignificant (less than 4.0 on the Richter scale). • Minor (4.0–4.9). • Damaging (5.0–5.9). • Destructive (6.0–6.9). • Major (7.0–7.9). • Great (over 8.0).
Earthquakes on the ocean floor can cause huge waves called tsunamis • A tsunami is a series of large waves generated when part of the ocean floor suddenly rises or drops. • Most large tsunamis are caused when certain types of faults in the ocean floor move up or down as a result of a large underwater earthquake, a landslide caused by such an earthquake, or in some cases by a volcanic eruption. • Tsunamis are often called tidal waves, although they have nothing to do with tides.
As the waves near land they slow to about 45 kilometers per hour but are squeezed upwards and increased in height. Waves move rapidly in deep ocean reaching speeds of up to 890 kilometers per hour. Waves head inland causing damage in their path. Earthquake in seafloor swiftly pushes water upwards, and starts a series of waves. Undersea thrust fault Upward wave Bangladesh India Myanmar Thailand Malaysia Sri Lanka Earthquake Sumatra Indonesia December 26, 2004, tsunami Fig. 12-8, p. 281
Earthquakes on the ocean floor can cause huge waves called tsunamis • They can travel far across the ocean at the speed of a jet plane. • In deep water the waves are very far apart—sometimes hundreds of kilometers—and their crests are not very high. • As a tsunami approaches a coast, it slows down, its wave crests squeeze closer together, and their heights grow rapidly. • Hits a coast as a series of towering walls of water that can level buildings.
Section 12-2 How are the earth’s rocks recycled?
There are three major types of rocks • A mineral is an element or inorganic compound that occurs naturally in the earth’s crust as a solid with a regular internal crystalline structure. • A few minerals consist of a single element such as gold, silver, and diamond (carbon). • Most of the more than 2,000 identified minerals occur as inorganic compounds formed by various combinations of elements, such as salt (sodium chloride or NaCl) and quartzite (silicon dioxide or SiO2).
There are three major types of rocks • Rock is a solid combination of one or more minerals found in the earth’s crust. • Some kinds of rock, such as limestone and quartzite, contain only one mineral while most consist of two or more minerals, such as granite—a mixture of mica, feldspar, and quartz crystals. • Three broad classes: • Sedimentary rock (e.g. sandstone, limestone). • Igneous rock (e.g. granite). • Metamorphic rock (e.g. slate, marble).
Erosion Transportation Weathering Deposition Igneous rock Granite, pumice, basalt Sedimentary rock Sandstone, limestone Heat, pressure Cooling Heat, pressure, stress Magma (molten rock) Melting Metamorphic rock Slate, marble, gneiss, quartzite Fig. 12-10, p. 283
Section 12-3 What are mineral resources and what are the environmental effects of using them?
We use a variety of nonrenewable mineral resources • A mineral resource is a concentration of naturally occurring material from the earth’s crust that can be extracted and processed into useful products and raw materials at an affordable cost. • Found and extracted more than 100 minerals from the earth’s crust. • Examplesare fossil fuels (such as coal), metallic minerals (such as aluminum and gold), and nonmetallic minerals (such as sand and limestone). • Minerals are classified as nonrenewable resources.
We use a variety of nonrenewable mineral resources • An ore is rock that contains a large enough concentration of a particular mineral—often a metal—to make it profitable for mining and processing. • High-grade ore contains a large concentration of the desired mineral. • Low-grade ore has a smaller concentration. • Aluminum (Al) is used for packaging and beverage cans and as a structural material in motor vehicles, aircraft, and buildings.
We use a variety of nonrenewable mineral resources • Steel, an essential material used in buildings and motor vehicles, is a mixture (alloy) of iron (Fe) and other elements that are added to give it certain properties. • Copper (Cu), a good conductor of electricity, is used for electrical and communications wiring. • Gold (Au) is used in electrical equipment, tooth fillings, jewelry, coins, and some medical implants.
Surface mining Melting metal Smelting Metal ore Separation of ore from gangue Conversion to product Discarding of product Recycling Stepped Art Fig. 12-11, p. 285
There are several ways to remove mineral deposits • Shallow mineral deposits are removed by surface mining by: • Removing vegetation. • Removing the overburden or soil and rock overlying a useful mineral deposit. • Placing waste material set aside in piles, called spoils. • Open-pit mining.
Harmful effects of extraction, processing, and use of nonrenewable mineral or energy resources
Types of miningOpen pit, strip, contour strip, and mountaintop removable
Undisturbed land Overburden Highwall Coal seam Overburden Pit Bench Coal seam Spoil banks Fig. 12-15, p. 287
Section 12-4 How long will supplies of nonrenewable mineral resources last?
Mineral resources are distributed unevenly • The earth’s crust contains fairly abundant deposits of iron and aluminum. • Manganese, chromium, cobalt, and platinum are relatively scarce. • The earth’s geologic processes have not distributed deposits of nonrenewable mineral resources evenly among countries.
Section 12-5 How can we use mineral resources more sustainably?
Three big ideas • Dynamic forces that move matter within the earth and on its surface recycle the earth’s rocks, form deposits of mineral resources, and cause volcanic eruptions, earthquakes, and tsunamis. • The available supply of a mineral resource depends on how much of it is in the earth’s crust, how fast we use it, the mining technology used to obtain it, its market prices, and the harmful environmental effects of removing and using it. • We can use mineral resources more sustainably by trying to find substitutes for scarce resources, reducing resource waste, and reusing and recycling nonrenewable minerals.
End of “Short Version” • The slides that follow are those taken out of the “long version” of this same lecture. You should still read the following slides for better understanding, but I will not go over them in class unless you have specific questions.
Volcanoes release molten rock from the earth’s interior • An active volcano occurs where magma reaches the earth’s surface through a central vent or a long crack, called a fissure. • Many volcanoes form along the boundaries of the earth’s tectonic plates when one plate slides under or moves away from another plate. • Magma that reaches earth’s surface is called lava. • Volcanic activity can release large chunks of lava rock, glowing hot ash, liquid lava, and gases into the environment.
Earthquakes are geological rock-and-roll events • The largest recorded earthquake occurred in Chile on May 22, 1960 and measured 9.5 on the Richter scale. • The primary effects of earthquakes include shaking and sometimes a permanent vertical or horizontal displacement of the ground. These effects may have serious consequences for people and for buildings, bridges, freeway overpasses, dams, and pipelines.
Earthquakes are geological rock-and-roll events • One way to reduce the loss of life and property damage is to examine historical records and make geologic measurements to locate active fault zones. • Map high-risk areas and establish building codes that regulate the placement and design of buildings in such areas. • People evaluate the risk and factor it into their decisions about where to live. • Engineers know how to make buildings and structures more earthquake resistant.