Earth’s Structure
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Transcript of Earth’s Structure
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Earth’s Structure
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• Radioactive dating techniques provide data that indicates the Earth was formed approximately 4.6 billion years ago.
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• As the Earth cooled, chemical reactions resulted in the production of the layers of the earth that exist today. These include a metal-rich inner and outer core and a silicate-rich crust and mantle.
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Crust• The crust is the outermost layer of the Earth. It is also the
thinnest layer and is divided into two types as shown below.
• The crust is composed mainly of silicon, oxygen and aluminum.
Continental Crust Oceanic Crust35-70 km thick Up to 8 km thick3,500 million to 4 billion years old Up to 200 million years oldDensity is about 2.7 g/cm3 Density is about 3 g/cm3
Igneous and sedimentary rocks Igneous rock (like basalt)
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Mantle• The mantle, the largest layer of the Earth is just below
the crust. The mantle has a thin, sedimentary layer of rock at the top, but under that is mainly magma.
• Magma is molten rock from the center of the Earth. The Mantle is hotter and denser because pressure inside the Earth increases with depth.
• The mantle is composed primarily of iron, magnesium, aluminum and silicon.
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Core
• The core is nearly twice as dense as the mantle because its composition is metal (iron and nickel) rather than rocky.
• The core is made of two parts, a liquid outer core and a solid inner core.
• It is thought that the Earth’s magnetic field is created by the spinning of the liquid outer core as the Earth rotates.
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2,900 km
2,200 km
Crust
35 – 70 km
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Three Types of Rock1. Igneous– Formed at the surface from lava or . . . – Formed inside the crust from magma that has
cooled.– Examples: granite and basalt
Granite on basalt sculpture
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1. Igneous continued– Slow cooling igneous rock
(inside the earth’s crust), allows the formation of large crystals of individual minerals. (plutonic/intrusive)
– Fast cooling igneous rock (outside the earth’s crust) has a smooth texture with small crystals. (volcanic/extrusive)
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2. Sedimentary Rock• Formed from weathering and erosion or from
precipitated fragments that have been bound under pressure.
• Examples: Limestone or sandstone• Sedimentary rock is the most common
source of fossils.
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Wisconsin Dells
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3. Metamorphic Rock
• Is formed under conditions of extreme temperature and pressure change.
• Examples: Gneiss and marble
• Note: If too much temperature and pressure exist, the rock will melt and become igneous.
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• Marble cliff along the Shakadang Trail, Taiwan
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The Rock Cycle
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