Unit 5: Part I Geologic Processes 1

Key Concepts of Geology for the AP Exam Earth’s Geologic History Earth’s Structure & Composition Plate Tectonics & Boundaries/Movements Volcanic Activity & Hotspots Earthquakes Weathering & Erosion The Rock Cycle 2

EARTH’S HISTORY *Availability of Earth’s resources was determined when the planet was formed and cooled* 4.6 Billion years ago, after the birth of the star called Sun, dust and rocks accumulated in a spherical mass. Early Earth was a hot, boiling sea of magma where heat had been generated by the collisions of smaller rock that collided and clumped together Oldest rocks geologists have been able to find are 3.9 billion years old. Collisions tapered off, Earth began to cool and a thin crust formed at the surface.

Earth’s History As the cooling continued, water vapor began to escape and condense in the earth's early atmosphere, forming clouds and rain. This water would cool the surface further until it was flooded with water, forming the seas. As Earth rotated, heavier elements like Iron were pushed towards the center and the lighter elements like Silicon remained closer to the surface. Earth is dynamic and ever-changing: New mountains form, old ones wear down, volcanoes melt and reshape new crust

Ole Ally Weg (Not an actual nickname) German physicist & Climatologist Proposed “Continental Drift Theory” in 1912 Large landmasses fit like a puzzle Similar rock structures Identical plant fossils on coasts of “matching continents” His theory is now called “Theory of Plate Tectonics”

Pangea

The Tectonic Cycle Theory of Plate Tectonics PRODUCES: VOLCANOES and EARTHQUAKES OCEANIC RIDGE SYSTEM MOUNTAINS & TRENCHES TRENCHES

The Earth Is a Dynamic Planet GEOLOGY: Dynamic Processes occurring on Earth’s surface and interior Three major concentric zones Core – solid inner core and liquid outer core Mantle- middle Includes the ASTHENOSPHERE (partly melted flowing rock) Crust- Continental crust (Granite) Oceanic crust (Basalt): 71% of crust 8

Earth’s Vertical Zonation

1. Oceanic crust – floor of deep ocean basins Lithosphere - Earth’s crust & upper mantle Thickness varies from 10 to 200 km 1. Oceanic crust – floor of deep ocean basins Composed of basalt (igneous). Also iron, magnesium and calcium. Thin (4-5 km) and young. 2. Continental crust -- forms continents. Composed of granite (igneous). Also silicon, aluminum, sodium and potassium. Thickness 35 to 70 km. Old crust.

The Lithosphere The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere.

The Crust The crust is composed of two rocks. The continental crust is mostly granite. The oceanic crust is basalt. Basalt is much denser than the granite. Because of this, the less dense continents ride on the denser oceanic plates.

The Mantle The Mantle is the largest layer of the Earth. The middle mantle is composed of very hot dense rock that flows like asphalt under a heavy weight. The movement of the middle mantle (asthenosphere) is the reason that the crustal plates of the Earth move.

Convection Currents The middle mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again --repeating this cycle over and over.

Convection Currents The next time you heat anything like soup or water in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the asthenosphere they also move the crust. The crust gets a free ride with these currents, like the cork in this illustration.

The Outer Core The core of the Earth is like a ball of very hot metals. The outer core is so hot that the metals in it are all in the liquid state. The outer core is composed of the melted metals of nickel and iron.

The Inner Core The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place like a solid. (Ni, Fe, Au, Pt and U)

Mantle (asthenosphere) Volcanoes Folded mountain belt Abyssal floor Oceanic ridge Abyssal floor Abyssal hills Trench Craton Abyssal plain Oceanic crust (lithosphere) Abyssal plain Continental shelf Continental slope Continental rise Mantle (lithosphere) Continental crust (lithosphere) Mantle (lithosphere) Figure 14.2 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)

PLATES BOUNDARIES & MOVEMENT Move at about the rate a fingernail grows

Collision between two continents Spreading center Ocean trench Oceanic tectonic plate Oceanic tectonic plate Plate movement Collision between two continents Plate movement Tectonic plate Subduction zone Oceanic crust Oceanic crust Continental crust Continental crust Cold dense material falls back through mantle Material cools as it reaches the outer mantle Mantle convection cell Hot material rising through the mantle Figure 14.3 The earth’s crust is made up of a mosaic of huge rigid plates, called tectonic plates, which move very slowly across the asthenosphere in response to forces in the mantle. See an animation based on this figure at CengageNOW™. Two plates move towards each other. One is subducted back into the mantle on a falling convection current. Mantle Hot outer core Inner core Fig. 14-3, p. 346

m EURASIAN PLATE NORTH AMERICAN PLATE ANATOLIAN PLATE JUAN DE FUCA PLATE CHINA SUBPLATE CARIBBEAN PLATE PHILIPPINE PLATE ARABIAN PLATE AFRICAN PLATE INDIA PLATE PACIFIC PLATE PACIFIC PLATE COCOS PLATE SOUTH AMERICAN PLATE NAZCA PLATE AUSTRALIAN PLATE SOMALIAN SUBPLATE Figure 14.4 The earth’s major tectonic plates. See an animation based on this figure at CengageNOW. Question: What plate are you riding on? SCOTIA PLATE ANTARCTIC PLATE Divergent plate boundaries Convergent plate boundaries Transform faults Fig. 14-4, p. 347

Transform Fault Boundaries 2 plates SLIDE PAST one another Example: San Andreas Fault

The San Andreas Fault as it crosses part of the Carrizo Plain in California, U.S. 25

Convergent Plate Boundaries 2 Plates COLLIDE Crust is destroyed and recycled back into Earth’s interior as one of the plates dives under another Called SUBDUCTION ZONES VOLCANOES & MOUNTAINS found here Three types of convergent boundaries 1. Oceanic-Oceanic 2. Oceanic-Continental 3. Continental-Continental

Convergent Boundaries Oceanic meets Oceanic: 2 oceanic plates converge; one is usually subducted under the other and in the process a deep oceanic trench is formed. Example: The Marianas Trench (Phillipine Plate subducting under the Pacific Plate) Also forms undersea volcanoes that lead to the formation of island chains Oceanic meets Continental: Oceanic plate pushes into and subducts under (more dense) a continental plate, the overriding continental plate is lifted up and a mountain range is created. Ex: Andes Mountains (Oceanic Nazca plate subducted under South American plate) Continental meets Continental : 2 continental plates meet, neither is subducted because the continental rocks are equally dense. Instead, the crust tends to buckle and be pushed upward or sideways. Example: The Himalaya Mountain chain (Eurasian plate crumples and overrides the Indian plate) Example: Appalachian Mountains (North American, Eurasian, & African plates)

Convergent Plates: Mt. Everest

Everest (Not the University) Mt Everest is the tallest mountain At 29,029 ft (That is 5.5 MILES!) It grows 1.6-3.9 inches higher every year Everest is part of the Himalaya mountain range along the border of Nepal and Tibet. At 9,800 feet, for example, there's about 2/3 of the oxygen in the air than at sea level. At 20,000 ft, there is roughly half the oxygen content in the air. At 29,035ft, the summit of Everest, there is only a third of the oxygen in the air.

Convergent Boundaries: Andes Mountains (Peru)

Divergent Plate Boundaries Form ridges in ocean (ex: Mid-Atlantic Ridge) North American & Eurasian plate diverging Form rifts on land (ex: Great African Rift Valley)

Divergent Plates: Building New Crust

Divergent Boundary: Mid-Atlantic Ridge System

Divergent Boundary: Africa’s Great Rift Valley

Earth’s Surface Builds Up and Wears Down Internal geologic processes build up the surface External geologic processes (driven by the sun and influenced by gravity) Weathering (key in soil formation) Physical, Chemical, and Biological processes that break down rock Erosion Wind, Water, Human Activities Glaciers- (formed the Great Lakes) 36

Parent material (rock) Biological weathering (tree roots and lichens) Chemical weathering (water, acids, and gases) Physical weathering (wind, rain, thermal expansion and contraction, water freezing) Figure 14.6 Weathering: Biological, chemical, and physical processes weather or convert rock into smaller fragments and particles. It is the first step in soil formation. Particles of parent material Fig. 14-6, p. 348

Volcanoes: Molten Rock Release from Interior A fissure (vent or crack) in Earth’s surface that releases molten rock from the interior. Magma (molten rock beneath the surface) Lava (molten rock above the surface) Usually found in areas with earthquake activity Benefits: Form mountains, lakes, islands, fertile soil 38

Volcanic Ash Consists of rock fragments, minerals, gas Formed from dissolved gas in magma being released violently Number of negative effects Can change local climates by preventing solar radiation from reaching Earth’s surface Reduce crop yields

Partially molten asthenosphere Extinct volcanoes Eruption cloud Ash Acid rain Ash flow Lava flow Mud flow Central vent Landslide Magma conduit Magma reservoir Figure 14.7 A volcano is created when magma in the partially molten asthenosphere rises in a plume through the lithosphere to erupt on the surface as lava, which builds a cone. Sometimes, internal pressure is high enough to cause lava, ash, and gases to be ejected into the atmosphere or to flow over land, causing considerable damage (Concept 14-1B). Chains of islands have been created by volcanoes that erupted and then became inactive. Solid lithosphere Upwelling magma Partially molten asthenosphere Fig. 14-7, p. 349

AGHHHHHHHH RUN

Mount St. Helens (1980) 1980-Eruption

Mount Pinutubo (Phillippines-1991)

Tectonic Activity

EARTHQUAKES Earthquake Terminology (MUST KNOW THESE TERMS) Seismic waves- vibrations caused by earthquakes Focus : Point of initial movement Epicenter: Point on the surface above the focus Magnitude – amount of energy released Amplitude – size of seismic waves 45

Earthquakes Earthquakes caused by stress in crust which deforms rock until it fractures producing faults. This faulting or abrupt movement causes EARTHQUAKES

Earthquakes Richter scale – a logarithmic scale recorded by a seismograph. Measures the amplitudes of the waves produced. Ex: An earthquake of magnitude 5 has 10X more ground shaking than a magnitude of 4. It is the energy that knocks down buildings and causes damage. Insignificant: <4.0 Destructive: 6.0–6.9 Major: 7.0–7.9 Great: >8.0 47

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 Figure 14.8 Major features and effects of an earthquake, one of nature’s most powerful events. Shock waves Focus Epicenter Fig. 14-8, p. 350

Earthquakes AFTERSHOCKS– smaller earthquakes that follow – often over a period of months FORESHOCKS – seconds to weeks before the main shock PRIMARY EFFECTS - shaking, sometimes permanent vertical or horizontal displacement of earth SECONDARY EFFECTS - rock slides, fires, flooding, tsumanis 49

Earthquakes Can Cause Landslides Mass wasting Slow movement or Fast movement Rockslides Avalanches Mudslides 1970, earthquake in Peru caused massive landslide that killed 17,000 people 50

Quake Risk in the USA 51

What about in GA?

Quake Risk Worldwide 53

Interesting Facts There are over 1 million eq a year There are over 10,000 eq in California a year. San Andreas Fault is over 800 miles long.

Tsunamis Caused by earthquakes in the sea Tsunami (tidal wave) Can travel as fast as a jet plane Detection of tsunamis by buoys 55

Undersea thrust fault Upward wave Bangladesh India Burma Thailand Earthquake in seafloor swiftly pushes water upwards, and starts a series of waves Waves move rapidly in deep ocean reaching speeds of up to 890 kilometers per hour. As the waves near land they slow to about 45 kilometers per hour but are squeezed upwards and increased in height. Waves head inland causing damage in their path. Undersea thrust fault Upward wave Bangladesh India Burma Figure 14.11 Formation of a tsunami and map of area affected by a large tsunami in December 2004. Thailand Malaysia Sri Lanka Earthquake Indonesia Sumatra December 26, 2004, tsunami Fig. 14-11, p. 352

2004: Indonesia Tsunami December 26, 2004: Indian Ocean Magnitude of 9.15 earthquake Waves as high as 100 feet, 228,000 were killed Coral reefs and mangrove forests reduce wave impact. (mangrove forests had been cleared and many reefs have been damaged in last 30 years)

Indonesian Shoreline Before and After 58

2011: Japanese Tsunami March 11, 2011: Tohoku Earthquake and Tsunami Occurred off coast of Japan 9.3 magnitude; 20 miles under water 133 foot waves Additional Complication: Nuclear Power Facility

The Rock Cycle Concept 3 The three major types of rocks found in the earth’s crust—sedimentary, igneous, and metamorphic—are recycled very slowly by the process of erosion, melting, and metamorphism. 60

Minerals Either an ELEMENT or INORGANIC COMPOUND – naturally occurring and a solid Some are single elements – Au, Ag Most are compounds – mica, salt, quartz

ROCKS Any material that makes up a large natural continuous part of the earth’s crust Can contain only one mineral but most consist of two or more minerals Example: GRANITE – quartz, mica, and feldspar

3 Types of Rocks Sedimentary Made of sediments- clastic -cemented and compacted chemical- made from dissolved minerals like limestone and rock salt) Sandstone and shale (compacted sediments) Dolomite and limestone (compacted shells and skeletons) Lignite and bituminous coal (compacted plant remains) 63

3 Types of Rocks Igneous – forms the bulk of earth’s crust Granite (formed underground) Pumice Obsidian Basalt Metamorphic –formed by heat and pressure Anthracite from coal Slate from shale Marble from limestone Gneiss from granite 64

IGNEOUS ROCKS FORMS FROM MOLTEN ROCK MATERIAL (MAGMA) FORMS FROM LAVA Wells up from upper mantle or deep crust Cools Hardens into rock – EXAMPLE: GRANITE FORMS FROM LAVA Forms above ground when magma coold Main part of earth’s crust Source of many nonfuel mineral resources

The Rock Cycle

The Rock Cycle