Volcanoes Presentation was made by Irina Tishchenko Form 10 B
The definition of volcanoes A volcano is a mountain that opens downward to a pool of molten rock below the surface of the earth.
What causes volcanoes to erupt? n The Earth's crust is made up of huge slabs called plates, which fit together like a puzzle. These plates sometimes move. n Between the Earth's crust and the mantle is a substance called magma which is made of rock and gases. n When two plates collide, one section slides on top of the other, the one beneath is pushed down. Magma is squeezed up between two plates.
Magma and lava n Magma – molten rock beneath the surface n Lava – erupted magma lava A a Pahoe
Types of volcanoes Scientists put volcanoes into three groups: q An Active volcanoes one that is erupting or will soon erupt. q A Dormant volcanoes one that has not erupted for a long time. q An Extinct volcanoes one that has not erupted for more than 10. 000 years.
Volcanic landforms n Cinder cones n Composite volcanoes n Shield volcanoes
Cinder cones volcanoes n Has tall, very steep sides. n Has explosive eruptions. n This eruption produces a lot of cinder and ash.
Shield volcanoes n Is wide and somewhat flat. n It forms from a quiet eruption. n Lava flows out quietly and for great distances.
Composite volcanoes n Form from explosive eruptions. n Produce a lot of lava and ash. n Is small, with steep sides.
The largest active volcano n The world's largest, active volcano is Mauna Loa in Hawaii, where famous coffee is grown in the rich volcanic soils. Mauna Loa is 13, 677 feet above sea level. From its base below sea level to its summit, Mauna Loa is taller than Mount Everest.
Underwater volcanoes n The floor of the ocean is similar to dry land. There are flat plains, mountain ridges, canyons and trenches in the ocean floor. There are more volcanoes under the oceanthan on the land
Volcanologists n Special scientists are called volcanologists. They study volcanoes in different ways. This helps to learn about the volcanos history and to know what it is going to do.
How do volcanoes affect the Earth? n hot ash can flow really quickly n knock down buildings n dam rivers (flooding/drought) n kill crops and livestock n ash and Gases can block sunlight n drop average global temperature noticeably
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