Transcript File
Layers of the Earth The Earth’s Interior Most scientists agree that soon after Earth’s formation, Earth was a large ball of molten (melted) rock. As time passed, the molten materials cooled, hardened, and separated into layers. Composition (What it is made of) • Crust • Mantle • Core The Crust • Thin, outer layer that covers the planet • 8 - 32 km thick • 2 types of crust – Oceanic (very dense, made of basalt) – Continental (less dense, made of granite) Oceanic and Continental Crust The Mantle • Middle layer • Very thick layer (2900 km thick) • Made of silicon, oxygen, iron, magnesium - solid that has the ability to flow = plasticity The Core • • • • Central part of the planet Made of iron and nickel 1/3 of the earth’s mass Very hot - inner core = solid - outer core = liquid Earth’s Layers • How are the earth’s layers similar to an egg? • Shell=crust • Egg white=mantle • Yolk=core Physical Structure of the Earth (5 Layers) • Lithosphere- rigid outer layer (crust) • Asthenosphere- solid rock that flows slowly (like hot asphalt) • Mesosphere- middle layer • Outer Core- liquid layer • Inner Core- solid, very dense Do scientists travel to the inside of Earth to learn about the layers? • High temperatures and tremendous pressure in the Earth’s interior would make traveling there and remaining alive impossible. • Even the deepest oil wells are only a few kilometers deep, and the diameter of the Earth is 12,756 km. So, how do we know about the layers? The study of behaviors of seismic waves has allowed geologists to piece together information about the parts of Earth that man has never seen directly. When earthquakes occur, vibrations are sent out through the Earth. These vibrations are called seismic waves. Seismic Waves • Seismic waves can travel along the surface of the Earth or through its interior. • The waves speed up, slow down, or stop depending on the type of material (medium) that they are passing through. For example: S-waves are a type of seismic wave that can't go through liquid. Therefore, scientists know that the part of the Earth that S-waves can't penetrate is made up of liquid. The Inner Core The deepest layer in Earth is the inner core. It is located at the center of Earth because it contains the densest material of all of Earth’s layers. The inner core is solid and mostly composed of the element iron (Fe). Its extremely hot temperature is estimated at 6,000 °C. This layer is approximately 1,250 km thick. The Outer Core The outer core is less dense than the inner core and, therefore, is located around the inner core. The temperatures range from 4,000 °C to 5,000 °C. The outer core is approximately 2,200 kilometers thick and is a combination of mostly liquid iron (Fe) and nickel (Ni). The Mantle and Asthenosphere The mantle is located outside the outer core. This layer is mostly made of iron (Fe) and magnesium (Mg) and has a thickness of approximately 2,900 kilometers. The upper mantle’s high temperatures of 2,800–3,200 °C can melt rocks. The upper part of the mantle is called the asthenosphere. The asthenosphere is a solid that flows like a liquid. This physical property is called plasticity. Scientists believe that the lithosphere and the crust are able to move slowly over the top of the mantle and asthenosphere. The Crust and Lithosphere The layer around the asthenosphere is known as the lithosphere. The lithosphere is the coolest, thinnest layer. This layer is made mostly of the elements oxygen (O2) and silicon (Si). Continental crust is thicker than oceanic crust. The crust is broken into many large pieces called tectonic plates. Scientists believe these plates “float” and move around very slowly on the semiliquid asthenosphere. Layers of the Earth Model 1. What doesthe marble represent? Why? 2. What do the 2 playdoh layers represent? Why? 3. What does the aluminum foil represent? Why?