Chapter 4 Book Notes

Seafloor crust and continental crust plates move in

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Seafloor crust and continental crust Plates move in concert with underlying mantle convection, driven by the heat released from Earth’s interior Over tens of millions of years, any piece of seafloor crust gradually makes its way across the ocean bottom, then finally gets recycled into the mantle in the process we call subduction
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In places where continental plates are pulling apart, the crust things and creates a large rift valley Places where slip sideways relative to each other are marked by what we call plate boundary faults Earthquakes can move plates by several meters in a few seconds Volcanic activity may occur any place where a plume of hot mantle material rises up to make what we call a hot spot All present-day continents were once all stuck together in a single “supercontinent” sometimes called Pangaea Conclusion: Plate tectonics plays a key role in explaining nearly all of Earth’s geological features. Why does Earth have a protective magnetic field? Gas molecules move fast enough that they exceed their world’s escape velocity and simply “take off” into space (thermal escape ) Jovian planets retain H because their large masses give them much higher escape velocities Impacts also blast atmospheric gas into space Gas can be lost through a mechanism known as solar wind stripping, which occurs when particles from the solar wind in effect sweep atmospheric gas particles into space A magnetic field can affect charged particles or magnetized objects in its vicinity Three basic requirements for global magnetic field: (1) An interior region of electrically conducting fluid (liquid or gas), such as molten metal (2) Convection in that layer of fluid (3) At least moderately rapid rotation of the planet The magnetic field protects Earth’s surface and atmosphere from most of the energetic particles of the solar wind because it creates a magnetosphere that acts like a protective bubble surrounding our planet Conclusion: Magnetosphere deflects particles while they are still high above our atmosphere and prevents solar wind from stripping Earth’s atmospheric gas away. How does the greenhouse effect make Earth habitable? Something must be making our planet much warmer than we would expect based on its distance from the Sun alone, and that something is what we call the greenhouse effect Some of visible light gets absorbed by the ground, while the rest is reflected back to space Ground returns energy in form of infrared light Gases that are particularly good at absorbing infrared light are called greenhouse gases Greenhouse gases: H20, CO2, CH4 Conclusion: Without the greenhouse effect, Earth would be frozen over. What regulates Earth’s climate?
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Seafloor crust and continental crust Plates move in concert...

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