Earthquakes and Volcanoes
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What are volcanoes? Volcanoes are just a mountain with an opening or vent in the top. Earth has more than 600 active volcanoes. They are all in a circle around the Pacific Ocean and they are called the ring of fire. Volcanoes come from Earth's hot interior. Most volcanoes start at 37 to 100 miles below the surface. Melted rock below the Earth's surface is called magma. After an eruption, a volcano usually collapses into a crater. A volcano erupts when magma escapes through a vent.
What is an earthquake? Earthquakes are caused by a sudden shift of Earth's crust. Some earthquakes happen at breaks called faults. Most fault lines lie deep below the surface, but some can be seen on the surface. The focus is the place in Earth where the energy of an earthquake is first released. The epicenter is the spot on the Earth's surface that is directly above the focus. Other earthquakes take place where plates move past each other. Earthquakes can be measured by how much damage they have caused. The Mercalli scale ranks earth quakes this way. The Mercalli scale uses Roman numerals 1 to 12. The Ritcher scale lists numbers or magnitudes. Each number shows an earthquake that releases about 30 times more energy than the number before it. For example a 5.0 earthquake releases about 30 times more than a 4.o earthquake. A 6.0 earthquake releases about 900 more times than a 4.0 earthquake.
What is an earthquake? Earthquakes are caused by a sudden shift of Earth's crust. Some earthquakes happen at breaks called faults. Most fault lines lie deep below the surface, but some can be seen on the surface. The focus is the place in Earth where the energy of an earthquake is first released. The epicenter is the spot on the Earth's surface that is directly above the focus. Other earthquakes take place where plates move past each other. Earthquakes can be measured by how much damage they have caused. The Mercalli scale ranks earth quakes this way. The Mercalli scale uses Roman numerals 1 to 12. The Ritcher scale lists numbers or magnitudes. Each number shows an earthquake that releases about 30 times more energy than the number before it. For example a 5.0 earthquake releases about 30 times more than a 4.o earthquake. A 6.0 earthquake releases about 900 more times than a 4.0 earthquake.