Weathering, Erosion, and Plate Tectonics The creation of Earth’s Face

Questions What forces and phenomena create the different features of the earth? What are tectonic plates? What are the three major Types of Plate Boundaries? What are the two external processes that change the earth’s surface? What are the different types of Weathering and Erosion?

Forces that change the Earth’s Surface There are two major geological processes that create features on the earth: Faulting and Plate Tectonics Weathering and Erosion They both take a long time to change the earth. Remember, nothing drastic on earth happens at human speeds.

Plate Tectonics 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. Tectonic plates: huge rigid plates that are moved with convection cells or currents by floating on magma or molten rock.

The Earth’s Major Tectonic Plates Figure 15-4

Plate Movement Tectonic Plates move in 1 on four ways. Spreading, or moving apart Subduction, or diving under another plate Collision, or crashing into one another Sliding past each other in a shearing motion

The Earth’s Major Tectonic Plates The extremely slow movements of these plates cause them to grind into one another at divergent plate boundaries, move apart at convergent 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

GEOLOGIC PROCESSES The San Andreas Fault is an example of a transform fault. A fault Line is created when rocks meet and lack flexibility. They crack under pressure and the fracture is called a FAULT. Figure 15-5

Results of Movement Earthquakes are a result of plate movement. The Richter Scale is used to measure the intensity of an earthquake. Tsunamis can result from earthquakes originating in the ocean. Volcanoes are often located along the boundaries of tectonic plates. Magma, gases, ash, and dust explode out of these vents in the earth’s surface. Ring of Fire is located along the rim of the Pacific Ocean and contains most volcanoes.

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

Weathering Three types of weathering: Physical Chemical Biological Big Rock becomes Small Rock due to wind, rain, and frost wedging. Frost wedging occurs when water freezes in between the pores of large sedimentary rocks. Chemical When a chemical reaction degrades or decomposes a rock. More common with rocks containing carbon and oxygen, like limestone. Biological Conversion of Rock and Minerals into smaller particles due to living thing. Lichens, Tree Roots, Earthworms.

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 15.6 Natural capital: physical, chemical, and biological processes can weather or convert rock into smaller fragments and particles. It is the first step in soil formation. Particles of parent material Fig. 15-6, p. 340

Erosion Erosion is another major external factor that changes the surface of the earth. Erosion is different from weathering because erosion deposits materials from one place to another. Four major examples of erosion: Glacial Movement and Melt Mass Wasting Water Erosion Wind Erosion

Glacial Movement and Mass Wasting The Movement of Glaciers grind away mountainsides and form basins to capture melted ice water The Great Lakes were formed using this method. Mass Wasting When Rock and soil masses become detached from underlying material and move downhill under the influence of gravity. Rockslides, Mudslides, and Landslides Clearing of Trees and other vegetation increase Mass Wasting Occurrences.

Water and Wind Erosion Water Erosion Wind Erosion Water picks up material and moves it down stream. Waves can also reduce or increase beaches. Wind Erosion Wind transports and deposits sediments. Wind speeds must reach a minimum of 11 miles per hour before sediment can be moved.