GEOLOGY and the Rock Cycle

GEOLOGIC PROCESSES The earth is made up of a core, mantle, and crust and is constantly changing as a result of processes taking place on and below its surface. The earth’s interior consists of: Core: innermost zone with solid inner core and molten outer core that is extremely hot. Mantle: solid rock, under which is the asthenosphere that is melted pliable rock. Crust: Outermost zone which underlies the continents. (Lithosphere)

Tectonic plate Inner core Spreading center Collision between two continents Oceanic tectonic plate Ocean trench Oceanic tectonic plate Plate movement Plate movement Tectonic plate Oceanic crust Oceanic crust Subduction zone Continental crust Continental crust Material cools as it reaches the outer mantle Cold dense material falls back through mantle Hot material rising through the mantle Mantle convection cell Figure 15.3 Natural capital: the earth’s crust is made up of a mosaic of huge rigid plates, called tectonic plates, which move around in response to forces in the mantle. 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. 15-3, p. 337

INTERNAL GEOLOGIC PROCESSES Huge volumes of heated and molten rock moving around the earth’s interior form massive solid plates that move extremely slowly across the earth’s surface due to convection currents. Tectonic plates: huge rigid plates that are moved with convection cells or currents by floating on magma or molten rock.

Oceanic crust (lithosphere) Abyssal plain Continental slope Folded mountain belt Volcanoes Abyssal plain Abyssal floor Oceanic ridge Abyssal floor Abyssal hills Trench Craton Oceanic crust (lithosphere) Abyssal plain Continental slope Continental shelf Continental rise Mantle (lithosphere) Continental crust (lithosphere) Mantle (lithosphere) Figure 15.2 Natural capital: major features of the earth’s crust and upper mantle. The lithosphere, composed of the crust and outermost mantle, is rigid and brittle. The asthenosphere, a zone in the mantle, can be deformed by heat and pressure. Mantle (asthenosphere) Fig. 15-2, p. 336

Earth orbit: 149,600,000 km (1.00 AU) from Sun diameter: 12,756.3 km mass: 5.972e24 kg Earth’s layers (depths in km) 0- 40 Crust 40- 2890 Mantle 2890-5150 Outer core 5150-6378 Inner core

Earth Earth’s mass (measured in 10^24 kg) atmosphere = 0.0000051 oceans = 0.0014 crust = 0.026 mantle = 4.043 outer core = 1.835 inner core = 0.09675

Earth’s Interior Core is made up mostly of iron/nickel Temperatures in core reach 7500 K The crust is primarily quartz. Taken as a whole, the Earth's chemical composition (by mass) is: 34.6% Iron 2.4% Nickel 29.5% Oxygen 1.9% Sulfur 15.2% Silicon 0.05% Titanium 12.7% Magnesium

The Earth’s Major Tectonic Plates Figure 15-4

Major Plates North American Plate South American Plate Antarctic Plate Eurasian Plate African Plate Indian-Australian Plate Nazca Plate Pacific Plate

Plate Movement The extremely slow movements of these plates cause them to grind into one another at convergent plate boundaries, move apart at divergent plate boundaries and slide past at transform plate boundaries. Figure 15-4

Figure 15.4 Natural capital: the earth’s major tectonic plates. The extremely slow movements of these plates cause them to grind into one another at convergent plate boundaries, move apart from one another at divergent plate boundaries, and slide past one another at transform plate boundaries. QUESTION: What plate are you floating on? Fig. 15-4, p. 338

INDIA-AUSTRALIAN PLATE EURASIAN PLATE NORTH AMERICAN PLATE ANATOLIAN PLATE JUAN DE FUCA PLATE CARIBBEAN PLATE CHINA SUBPLATE ARABIAN PLATE AFRICAN PLATE PHILIPPINE PLATE PACIFIC PLATE SOUTH AMERICAN PLATE NAZCA PLATE INDIA-AUSTRALIAN PLATE SOMALIAN SUBPLATE Figure 15.4 Natural capital: the earth’s major tectonic plates. The extremely slow movements of these plates cause them to grind into one another at convergent plate boundaries, move apart from one another at divergent plate boundaries, and slide past one another at transform plate boundaries. QUESTION: What plate are you floating on? ANTARCTIC PLATE Divergent plate boundaries Convergent plate boundaries Transform faults Fig. 15-4a, p. 338

Transform fault Rising magma Trench Volcanic island arc Craton Transform fault Lithosphere Rising magma Subduction zone Lithosphere Lithosphere Asthenosphere Asthenosphere Asthenosphere Figure 15.4 Natural capital: the earth’s major tectonic plates. The extremely slow movements of these plates cause them to grind into one another at convergent plate boundaries, move apart from one another at divergent plate boundaries, and slide past one another at transform plate boundaries. QUESTION: What plate are you floating on? Divergent plate boundaries Convergent plate boundaries Transform faults Fig. 15-4b, p. 338

Convergent Plate Boundary Two plates pushed together Oceanic + Continental = Subduction Zone Oceanic + Oceanic = Trench Continental + Continental = Mountain Range

Divergent Plate Boundary Plates moves apart from one another Oceanic plates form oceanic ridges

Transform Faults Plates slide and grind past one another along a fracture in the lithosphere

Benefits of volcanoes, earthquakes, and tsunamis Geological: Recycle rock and earth’s crust Form minerals Ecological: Speciation (due to isolation) Maintaining atmosphere thus climate Enrich soils = more food

Geologic Time Scale ~4.6 billion years ago: Earth believed to have formed, hot ball of rock 3.9 billion years ago: rainstorms 3.5 billion years ago: oceans, first living organisms

Geologic Eras Precambrian Era: 4.6 billion years ago- 545 million years ago 87% of Earth’s history Prokaryotes dominated First eukaryotes appeared ~ 1.5 billion years ago Simple multicellular organisms in seas Paleozoic Era: 545 million years ago – 248 million years ago “Explosion of life” Many types of invertebrates in shallow seas Early: earliest vertebrates Middle: amphibians Later: reptiles

Geologic Eras Mesozoic Era: 248 million years ago – 65 million years ago Triassic: mammals made first appearance Jurassic: “age of dinosaurs” Cretaceous: radiation of mammals and evolution of flowering plants Plate Tectonics: continental shift Cenozoic Era: 65 million years ago – now Mammals flourish Primates evolve Extinctions affect diversity Modern human species evolved ~200,000 years ago

EXTERNAL GEOLOGIC PROCESSES Surface processes Based largely on energy from the sun and gravity Tends to wear down Earth’s surface and produce a variety of landforms by the buildup of eroded sediment Erosion Weathering

Wearing Down and Building Up the Earth’s Surface Weathering is an external process that wears the earth’s surface down. Figure 15-6 23

EROSION Process by which material is dissolved, loosened or worn away from one part of the earth’s surface and deposited in other places Streams are most important agents of erosion

MINERALS, ROCKS, AND THE ROCK CYCLE The earth’s crust consists of solid inorganic elements and compounds called minerals that can sometimes be used as resources. Mineral resource: is a concentration of naturally occurring material in or on the earth’s crust that can be extracted and processed into useful materials at an affordable cost. 25

Nonrenewable mineral resources Fossil fuels (oil, natural gas, coal) Metallic minerals (Al, Cu, Fe) Nonmetallic minerals (sand, gravel, limestone)

Minerals and their Uses Metals Nonmetals Al- building, cans Steel- building Cu- conductor, electronics Mn, Co, Cr- used in alloys Pt- catalytic converters Sand- glass, concrete, bricks Gravel- roadbeds Limestone- roadbeds, natural buffer Phosphate salts- fertilizers

US consumption 8% of world population but use 75% of metals on earth Uses: cars, engines, appliances, weapons, satellites

ROCK A very slow chemical cycle recycles three types of rock found in the earth’s crust: Sedimentary rock (sandstone, limestone). Formed from sediment of pre-existing rocks that are weathered and eroded Metamorphic rock (slate, marble, quartzite). Formed when pre-existing rock is subjected to high temperatures or pressure Igneous rock (granite, pumice, basalt). Formed from cooled magma at or below earth’s surface 29

Erosion Transportation Heat, pressure, stress Magma (molten rock) Weathering Deposition Igneous rock Granite, pumice, basalt Sedimentary rock Sandstone, limestone Heat, pressure Cooling Heat, pressure, stress Magma (molten rock) Figure 15.8 Natural capital: the rock cycle is the slowest of the earth’s cyclic processes. The earth’s materials are recycled over millions of years by three processes: melting, erosion, and metamorphism, which produce igneous, sedimentary, and metamorphic rocks. Rock from any of these classes can be converted to rock of either of the other two classes, or can be recycled within its own class. QUESTION: List three ways that the rock cycle benefits your lifestyle. Melting Metamorphic rock Slate, marble, gneiss, quartzite Fig. 15-8, p. 343 30