Geothermal Energy

Geothermal Energy — page 5 — Chapter One HEAT FROM INSIDE EARTH Heat from Earth’s interior is produced mainly by the radioactive decay of elements in Earth’s crust and mantle and also by friction generated along the margins of continental plates It generates surface phenomena such as lava flows geysers fumaroles hot springs and mud pots INSIDE EARTH Earth is made up of three layers the core mantle and crust Temperatures and pressures rise with increasing increasing depth inside the planet At roughly 50 miles 80 kilometers below the surface the rock of the mantle is at about 2,500 degrees Fahrenheit 1,370 degrees Celsius and becomes partly molten Below about 150 to 200 miles 250 300 km the mantle is under 8

Geothermal Energy — page 6 — HEAT FROM INSIDE EARTH mantle 1 800 miles so much pressure that it becomes more rigid again Beneath the mantle the material becomes much denser and liquefies core Scientists believe that this 4 300 miles crust layer called the outer core 3 19 miles consists of up to 90 percent molten iron and nickel with some other elements such as sulfur mixed in Finally below about 3 200 miles 5 100 km is the inner core This hottest layer is estimated to be between 8 000°F and 12 000°F Earth's interior has three main about 4 400°C 6 600°C layers a relatively thin rocky Some of the heat in crust a thick mantle and a largely Earth's interior is left over molten core The measurements from the planet's formation provided are averages formation and some is released from the outer core as iron and nickel slowly solidifies Most of the heat though is believed to result from the decay of long lived radioactive elements such as potassium thorium and uranium 2014 Encyclopædia Britannica Inc

Geothermal Energy — page 7 — GEOTHERMAL ENERGY RADIOACTIVITY Radioactivity is a feature of certain types of matter All matter is made of chemical elements and elements are made of atoms Most atoms are stable That is they do not change over time Radioactive atoms however change over time Tiny subatomic particles and energy fly out of them naturally The particles and energy that are released are a form of radiation The atoms are changed a little bit each time they release something They keep giving off particles and energy until they are changed into a stable form That process is called decay The amount of time that each type of atom takes to decay varies greatly It can be less than a second or millions of years The measure of that rate is called a half-life This refers to the time required for one half of a group of atoms to decay into a stable form Astronomers believe that these radioactive elements elements were formed in supernovas catastrophic explosions of giant stars that occurred before the solar system was formed The uranium and other 10

Geothermal Energy — page 8 — HEAT FROM INSIDE EARTH elements mixed with the clouds of gas and dust that ultimately collected together to form Earth PLATE TECTONICS The crust and outermost mantle together are called the lithosphere from the Greek word lithos meaning meaning rock The lithosphere is broken into rigid blocks or plates that essentially float on the denser material underneath and drift up against alongside over or underneath other plates The plates and the North American Plate Eurasian Plate Eurasian Plate Arabian Plate Caribbean Plate Juan de Fuca Plate Philippine Plate Cocos Pacific Plate Plate Indo African Plate Nazca Plate Australian Plate South American Plate Antarctic Plate Scotia Plate Direction of plate movement 2011 EB Inc This map shows the tectonic plates that make up Earth's lithosphere Earthquakes and volcanoes often happen along plate boundaries

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