The Changing Earth

1. The Changing Earth StarrySkies.com

2. LAYERS OF THE EARTH Core Mantle Crust

3. The Earth’s Layers • Crust • Outer layer • Made of rock • Very thin - like the skin of an apple • Between 8 and 25 miles thick • Broken into pieces called plates http://www.ukooa.co.uk

4. TheEarth’sLayers • Mantle • Just beneath the Earth’s crust • Solid rock • Very hot – between 1600 and 4000 F • Some parts soft like melted candy • Largest layer of earth – around 1800 miles thick http://all3000.narod.ru/

5. TheEarth’sLayers • Core • Center layer of the Earth • Hottest layer – between 4000 and 9000 Fahrenheit • Outer core is liquid or molten iron • Inner core is solid iron because of the pressure • Approximately 2400 miles thick

6. Moving Crust • What are plates? • Rigid blocks of crust and upper mantle rock • Fit together like a jigsaw puzzle • 12 major plates • Float on soft rock of the mantle • Move a few centimeters each year Continental Drift Theory Pangea – “supercontinent”….split apart 200 million years ago

7. Plate Movement / Colliding Plates Places where plates crash or crunch together are called convergent boundaries. Plates only move a few centimeters each year, so collisions are very slow and last millions of years. Even though plate collisions take a long time, lots of interesting things happen. For example, in the drawing above, an oceanic plate has crashed into a continental plate. Looking at this drawing of two plates colliding is like looking at a single frame in a slow-motion movie of two cars crashing into each other. Just as the front ends of cars fold and bend in a collision, so do the "front ends" of colliding plates. The edge of the continental plate in the drawing has folded into a huge mountain range, while the edge of the oceanic plate has bent downward and dug deep into the Earth. A trench has formed at the bend. http://www.cotf.edu/ete/modules/msese/earthsysflr/plates3.html http://www.cotf.edu/

8. Plate Movement Sliding Plates Although transform boundaries are not marked by spectacular surface features, their sliding motion causes lots of earthquakes. The strongest and most famous earthquake along the San Andreas fault hit San Francisco in 1906. Many buildings were shaken to pieces by the quake http://www.cotf.edu/

9. Plate MovementPlates Pulling ApartAs plates pull apart valleys and volcanoes develop. Where a divergent boundary crosses the land, the rift valleys which form are typically 30 to 50 kilometers wide. Examples include the East Africa rift in Kenya and Ethiopia, and the Rio Grande rift in New Mexico. Where a divergent boundary crosses the ocean floor, the rift valley is much narrower, only a kilometer or less across, and it runs along the top of a midoceanic ridge. Examples include the Mid-Atlantic ridge and the East Pacific Rise. Remember, plate separation is a slow process. http://www.cotf.edu http://www.cotf.edu/ete/modules/msese/earthsysflr/plates3.html

10. Mountains • Highest landforms • Form when continental plates collide (highest mountains) or continental and oceanic plates collide. • Magma (hot soft rock) builds up along the cracks and forms long chains of mountains. http://www.geocraft.com Mountains like the Himalaya Range of Tibet resulted from the collision of the continents. About 50 millions years ago moving tectonic plates brought the continents of Asia and India into contact with one another. Such continental collisions build spectacular mountain ranges. http://www.geocraft.com

11. Volcanoes • Mountains formed by lava ( magma that reaches the earth’s surface) and ash • Chains of volcanoes form where continental and oceanic plates collide. • Some volcanoes form in the middle of plates over hot columns of magma. • Deep inside Earth, between the molten iron core and the thin crust at the surface, there is a solid body of rock called the mantle. When rock from the mantle melts, moves to the surface through the crust, and releases pent-up gases, volcanoes erupt. But why does this solid rock melt and come to the surface? Extremely high temperature and pressure cause the rock to melt and become liquid rock or magma. When a large body of magma has formed, it rises through the denser rock layers toward Earth's surface.

12. Caused by plates crushing together, scraping past each other or bend in along jagged boundaries • Earthquakes send out seismic waves (ripples like form on a pond) and they are measured using an instrument called a seismograph. • The Richter scale measures the strength. • Many occur along faults (breaks in the plates) • Click on the URL to see a demonstration of how an earthquake occurs. http://www.crustal.ucsb.edu/ics/understanding/elastic/rebound.html

13. What are Fossils? • Remains or traces of past life found in sedimentary rock • Scientists study fossils to find out about how the Earth has changed.

14. Click on this website to see different types of fossils. http://web.ukonline.co.uk/conker/fossils/what-is-a-fossil.htm Click on this website to see how fossils are made. http://web.ukonline.co.uk/conker/fossils/how-fossils-were-made.htm Click on this website for a good site to learn more about dinosaur fossils. http://www.enchantedlearning.com/subjects/dinosaurs/dinofossils/

15. Other Sites used in this Presentation The Earth’s Layers http://volcano.und.nodak.edu/vwdocs/vwlessons/lessons/Earths_layers/Earths_layers1.html  Landforms –http://www.geocities.com/monte7dco/archipelago.htm  Plate Tectonics http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml  BrainPop Plate Tectonics and Layers of the Earth, Fossils http://brainpop.com/  Divergent, Convergent, Transforming movement http://www.cotf.edu/ete/modules/msese/earthsysflr/plates1.html S. Herndon, Fall 2004