Transcript Document
Spaceship Earth: Our oasis in the emptiness of space: The dynamic planet Alfred Wegener (1903) suggested and presented evidence that the continents were once a single supercontinent, called Pangea, which divided ~ 200 Million years ago into Laurasia and Gondwanaland and later into the continents we see today (“continental drift”) Fossils of the land-bound lizard Lystrosaurus were found in Africa, Antarctica and India, suggesting that these continents were one landmass during the life-time of this critter Geologic evidence for “continental drift” Rocks of same age cross continents Distribution of warm-water fossils Topography of Earth Huge mountain ranges (ridges, like the Mid-Atlantic Ridge) circle the globe on the ocean floors The crust of Earth consists of 11 major tectonic plates Epicenters of major earthquakes tend to occur along ocean ridges and plate boundaries The directions of movement of the major plates of Earth Schematic diagram of an ocean spreading center: Symmetry in magnetic reversals indicates sea-floor spreading. Elongated convection cells in the plastic asthenosphere drive the overlying rigid lithospheric plates. The Hawaiian island chain is a wonderful example of plate tectonics in the middle of a plate. It is fed by a stationary mantle plume under Loihi, and the Pacific Plate glides over it at a speed of ~ 5 cm/year, carrying the islands with it in a northwesterly direction. Ages of the Hawaiian islands: An example of plate tectonics associated with a mantle plume Where were Earth’s continents in the geologic past? Volcanoes: Pages 53 - 62 • Volcanoes are found on the surface of Earth and Venus; Mars has fewer volcanoes with some signs of relatively recent volcanic activity. • The volcanoes on Jupiter's satellite Io have turned the satellite inside out; it is heated inside by the tidal flexing action of nearby massive Jupiter. • Volcanoes of ice may have created some of the features now frozen into the bright smooth surface of Neptune's largest moon, Triton; dark geyser-like plumes have been observed in the process of eruption on the satellite. Active volcanoes on Earth occur mostly along plate boundaries Fire fountaining at Pu’u O’o, Hawaii, which has been erupting since 1983 Summit caldera of Mauna Loa volcano, Hawaii: A basaltic shield volcano Pahoehoe lava flows at Pu’u O’o, Hawaii. A’a lava flows, Pu’u O’o, Hawaii. Lava from Pu’u O’o, Hawaii, enters the ocean. For more images, see: http://hvo.wr.usgs.gov/kilauea/update/#images Mt. Pinatubo, June 12th, 1991 An explosive Island Arc volcano in the Philippines Composite Volcanoes in the Andes (Chile) Maat Mons, Venus Rift zones on Venus Olympus Mons on Mars, the tallest mountain in the Solar System Olympus Mons on Mars, compared to the Hawaiian island chain 640 km Right: Eruption of the volcano Pele on Jupiter’s moon Io. Below: Top view of volcano Pele The volcanic plume (above) is 1,300 km wide and 600 km high. Water volcanism on Saturn’s moon Enceladus Dark, active nitrogen geysers on Neptune’s moon Triton. The constant direction of the black streaks hints at a very thin atmosphere. The interior structure of Earth and the polar wandering of its magnetic field.