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Andes Mountains, South America Evidence of Continental Drift . – Fossils of Glossopteris, a seed fern that resembled low shrubs, have been found on many continents, indicating that the areas had a single climate that was close to the equator. Earth’s Layers Layers of the Earth • There are two ways that scientists label the layers of the Earth. – Composition layers – Physical layers Composition (What it is made of) • Crust • Mantle • Core Earth’s Layers • How are the earth’s layers similar to an egg? • Shell=crust • Egg white=mantle • Yolk=core The Crust • • • • Outer layer 5-100 km thick Thinnest layer 2 types of crust – Oceanic (very dense, made of basalt) – Continental (less dense, made of granite) Oceanic and Continental Crust • Middle layer • Very thick layer • Roughly 2800 km thick • No one has ever drilled to the mantle • It is VERY hot • composed of silicate rocks that are rich in iron and magnesium • Even though its solid it can flow The Mantle Convection Currents Convection Currents Cause the Tectonic Plates to move Movement of these plates Cause: 1. Earth Quakes 2. Mountains 3. Volcanoes 4. Rift valleys 5. Tsunamis Tectonic Plates • Earth’s crust is broken into about 19 pieces • These plates move on top of the asthenosphere • Made mostly of Iron and Nickel • 1/3 of the earth’s mass • Very hot • The core’s diameter is about the size of Mars (6856 km ) The Core Physical Layers • The less familiar layers are the physical layers. • They are based on how the layer looks or acts. Physical Structure of the Earth • Lithosphere (Crust) - (15-300 km) rigid outer layer • The tectonic Plates • A combination of crust and the upper region of the mantle • Cold and brittle (easily broken) Physical Layers • Asthenosphere • weak sphere” (250 km) – Hard rock that acts like warm tar or honey – Ductile and highly Viscous • involved in plate tectonic movements Mesosphere • Layer found between the asthenosphere and the outer core Physical Layers Continued • Outer Core- (2200 km) – liquid layer • Inner Core- (diameter= 2456 km) • Solid, dense core of the planet • Densest layer of the planet Side by side comparison Crust Mantle Core Lithosphere Asthenosphere Outer Core Inner Core The “spheres” • Atmosphere – – – – Least dense layer of the Earth Made of mostly oxygen and nitrogen Surrounds the Earth Filters out harmful radiation • Biosphere – Layer that all life is in – Not a specific location, just anywhere life is found Hydrosphere – Density= ~1.0 g/mL • Describes the combined mass of water found on, under, and over the surface of a planet. • Approximately 75% of the Earth's surface, an area of some 361 million square kilometres (is covered by ocean. Interesting fact… • Did you know?... – The center of the Earth’s core is hotter than the surface of the sun. The temperature of Earth’s inner core reaches 6000 °C whereas the surface of the sun is roughly 5500 °C. • The sun’s core, however, is 15,000,000 °C