Could you watch an island grow? The islands of Hawaii Exploring Inside Earth Earth is constantly changing. Earth looks different today than it did millions of years ago. What’s inside Earth? Very hard to answer, because you cannot just dig a hole to the center of the Earth. You would have to dig over 6,000 kilometers to reach the center of the Earth. Geologists use two type of evidence Direct evidence – rock samples Indirect evidence – seismic waves Evidence From Rock Samples Study rocks from inside Earth Geologists have drilled holes up to 12 kilometers deep Geologists can suggest what conditions are deep inside Earth Forces deep inside Earth sometimes blast rock to the surface from depths more than 100 kilometers deep, providing more information. Evidence From Seismic Waves Indirect method of observation When earthquakes occur, they produce seismic waves The speed of the seismic waves and the paths they take reveal the structure of the planet From seismic waves they have learned that Earth’s interior has several layers A Journey to the Center of Earth 3 main layers of the Earth Crust Mantle Core Layers very in Size, Composition and Temperature The temperature is heat left over from the formation of the planet Radioactive substances inside Earth creates heat Weight from the rock above causes an increase in the pressure as you get deeper The Crust The Crust is Earth’s outer layer – land and ocean floor Thickest under high mountains, thinnest beneath the ocean Crust is 5 to 40 kilometers thick, up to 70 kilometers beneath mountains Oceanic crust is the crust beneath the ocean, made of rocks such as basalt Basalt – dark rock with a fine texture Continental crust – land is mainly granite Granite – light color with a coarse texture The Mantle About 40 kilometers beneath the surface, you cross into a solid material the mantle a layer of hot rock Mantle has 3 layers, very hot rock, about 3,000 kilometers thick, and layers based on physical characteristics Lithosphere uppermost part similar to the crust, The uppermost part of the mantle and the crust together form the rigid layer called the lithosphere Averages about 100 kilometers thick Asthenosphere below the lithosphere, hot and increased pressure Soft than the rock above Can bend like plastic Still solid rock The Lower Mantle Extends all the way to the Earth’s core Core The Core is mostly made of metals iron and nickel Two parts of the core liquid out core solid inner core Inner and outer core are about 3,486 kilometers thick Outer core and Inner Core Outer Core – layer of molten metal surrounding the inner core (Liquid) Inner Core – dense ball of solid metal, great pressure pressing the iron and nickel go much it cannot become liquid The Core and Earth’s Magnetic Field Scientists think that the liquid outer core creates the Earth’s magnetic field Magnetic field affects the whole Earth A compass needle aligns with the line of force in Earth’s magnetic field Questions 1. 2. 3. 4. 5. Why is it difficult to determine Earth’s inner structure? How are seismic waves used to provide evidence about Earth’s interior? List Earth’s three main layers. What is the difference between the lithosphere and the asthenosphere? In which layer is each located? Classify each of the following layers as liquid, solid, or solid but able to flow slowly: lithosphere, asthenosphere, lower mantle, outer core, inner core.