© 2010 Pearson Education, Inc. Erosion of Craters Details of some craters suggest they were once filled with water.

© 2010 Pearson Education, Inc. Martian Rocks Mars rovers have found rocks that appear to have formed in water.

© 2010 Pearson Education, Inc. Hydrogen Content Map of hydrogen content (blue) shows that low- lying areas contain more water ice.

© 2010 Pearson Education, Inc. Crater Walls Gullies on crater walls suggest occasional liquid water flows have happened less than a million years ago.

© 2010 Pearson Education, Inc. “Seeing” the Surface Geology of Venus Its thick atmosphere forces us to explore Venus’s surface through radar mapping.

© 2010 Pearson Education, Inc. Cratering on Venus Venus has impact craters, but fewer than the Moon, Mercury, or Mars.

© 2010 Pearson Education, Inc. Volcanoes on Venus It has many volcanoes, including both shield volcanoes and stratovolcanoes.

© 2010 Pearson Education, Inc. Tectonics on Venus The planet’s fractured and contorted surface indicates tectonic stresses.

© 2010 Pearson Education, Inc. Erosion on Venus Photos of rocks taken by landers show little erosion.

© 2010 Pearson Education, Inc. Does Venus have plate tectonics? Venus does not appear to have plate tectonics, but entire surface seems to have been “repaved” 750 million years ago.

© 2010 Pearson Education, Inc. Earth’s Destiny Many of Earth’s features are determined by its size, rotation, and distance from Sun. The reason for plate tectonics is not yet clear.

© 2010 Pearson Education, Inc. Earth’s Destiny Many of Earth’s features are determined by its size, rotation, and distance from Sun. The reason for plate tectonics is not yet clear.

© 2010 Pearson Education, Inc. Earth’s Destiny Many of Earth’s features are determined by its size, rotation, and distance from Sun. The reason for plate tectonics is not yet clear.

© 2010 Pearson Education, Inc. Plate Tectonics on Earth Earth’s continents slide around on separate plates of crust.

© 2010 Pearson Education, Inc. How do we know that Earth’s surface is in motion?

© 2010 Pearson Education, Inc. Continental Motion Motion of the continents can be measured with GPS.

© 2010 Pearson Education, Inc. Continental Motion The idea of continental drift was inspired by the puzzle-like fit of the continents. Mantle material erupts where the seafloor spreads.

© 2010 Pearson Education, Inc. Seafloor Crust Thin seafloor crust differs from thick continental crust. Dating of the seafloor shows that it is usually quite young.

© 2010 Pearson Education, Inc. How is Earth’s surface shaped by plate tectonics?

© 2010 Pearson Education, Inc. Seafloor Recycling Seafloor is recycled through a process known as subduction.

© 2010 Pearson Education, Inc. Surface Features Major geological features of North America record the history of plate tectonics.

© 2010 Pearson Education, Inc. Surface Features The Himalayas formed from a collision between plates.

© 2010 Pearson Education, Inc. Surface Features The Red Sea is formed where plates are pulling apart.

© 2010 Pearson Education, Inc. Rifts, Faults, Earthquakes The San Andreas fault in California is a plate boundary. Motion of plates can cause earthquakes.

© 2010 Pearson Education, Inc. Plate Motions Measurements of plate motions tell us past and future layout of the continents.

© 2010 Pearson Education, Inc. Hot Spots The Hawaiian islands have formed where a plate is moving over a volcanic hot spot.

© 2010 Pearson Education, Inc. Carbon Dioxide Cycle 1.Atmospheric CO 2 dissolves in rainwater. 2.Rain erodes minerals that flow into ocean. 3.Minerals combine with carbon to make rocks on ocean floor.

© 2010 Pearson Education, Inc. Carbon Dioxide Cycle 4.Subduction carries carbonate rock down into mantle. 5.Rock melts in mantle and CO 2 is outgassed back into atmosphere through volcanoes.

© 2010 Pearson Education, Inc. Radiation Absorption in the Earth’s Atmosphere Solar X-rays are absorbed high in the atmosphere Solar ultraviolet light is absorbed by ozone in the mid atmosphere Visible light reaches the ground and warms the surface

© 2010 Pearson Education, Inc. Why the Sky Is Blue Atmosphere scatters blue light from Sun, making it appear to come from different directions. Sunsets are red because red light scatters less.

© 2010 Pearson Education, Inc. Dangers of Human Activity Human-made CFCs in the atmosphere destroy ozone, reducing protection from ultraviolet radiation. Human activity is driving many species to extinction. Human use of fossil fuels produces greenhouse gases that can cause global warming.

© 2010 Pearson Education, Inc. Greenhouse Effect Visible light passes through the atmosphere and warms a planet’s surface. The atmosphere absorbs infrared light from the surface, trapping heat.

© 2010 Pearson Education, Inc. Global Warming Earth’s average temperature has increased by 0.5°C in past 50 years. The concentration of CO 2 is rising rapidly. An unchecked rise in greenhouse gases will eventually lead to global warming.

© 2010 Pearson Education, Inc. CO 2 Concentration Most of the CO 2 increase has happened in last 50 years!

© 2010 Pearson Education, Inc. Modeling of Climate Change Complex models of global warming suggest that recent temperature increase is consistent with human production of greenhouse gases.

© 2010 Pearson Education, Inc. Consequences of Global Warming Storms more numerous and intense Rising ocean levels; melting glaciers Uncertain effects on food production, availability of fresh water Potential for social unrest

© 2010 Pearson Education, Inc. What have we learned? What are terrestrial planets like on the inside? –All terrestrial worlds have a core, mantle, and crust. –Denser material is found deeper inside. What causes geological activity? –Interior heat drives geological activity. –Radioactive decay is currently main heat source. Why do some planetary interiors create magnetic fields? –Requires motion of charged particles inside a planet

© 2010 Pearson Education, Inc. What have we learned? What processes shape planetary surfaces? –Cratering, volcanism, tectonics, erosion How do impact craters reveal a surface’s geological age? –The amount of cratering tells us how long ago a surface formed. Why do the terrestrial planets have different geological histories? –Differences arise because of planetary size, distance from Sun, and rotation rate.

© 2010 Pearson Education, Inc. What have we learned? What geological processes shaped our Moon? –Early cratering is still present. –Maria resulted from volcanism. What geological processes shaped Mercury? –Had cratering and volcanism similar to Moon –Tectonic features indicate early shrinkage.

© 2010 Pearson Education, Inc. What have we learned? How did Martians invade popular culture? –Surface features of Mars in early telescopic photos were misinterpreted as “canals.” What are the major geological features of Mars? –Differences in cratering across surface –Giant shield volcanoes –Evidence of tectonic activity

© 2010 Pearson Education, Inc. What have we learned? What geological evidence tells us that water once flowed on Mars? –Some surface features look like dry riverbeds. –Some craters appear to be eroded. –Rovers have found rocks that appear to have formed in water. –Gullies in crater walls may indicate recent water flows.

© 2010 Pearson Education, Inc. What have we learned? What are the major geological features of Venus? –Venus has cratering, volcanism, and tectonics but not much erosion. Does Venus have plate tectonics? –The lack of plate tectonics on Venus is a mystery.

© 2010 Pearson Education, Inc. What have we learned? How do we know that Earth’s surface is in motion? –Measurements of plate motions confirm the idea of continental drift. How is Earth’s surface shaped by plate tectonics? –Plate tectonics is responsible for subduction, seafloor spreading, mountains, rifts, and earthquakes.

© 2010 Pearson Education, Inc. What have we learned? Was Earth’s geology destined from birth? –Many of Earth’s features are determined by its size, distance from Sun, and rotation rate. –The reason for plate tectonics is still a mystery.

© 2010 Pearson Education, Inc.