0:06 volcanoes are our most explosive
0:13 landforms able to eject molten rock and
0:17 clouds of thick ash high into the atmosphere
0:24 with devastating consequences [Music]
0:31 volcanoes mostly occur along destructive
0:33 and constructive plate boundaries where
0:36 plates are pushed together or dragged apart
0:36 apart [Music]
0:46 cracks or weaknesses allow magma to rise
0:47 up from below the Earth's crust [Music]
0:50 [Music]
0:53 pressure builds up which then releases
1:01 a volcanic eruption [Music]
1:06 LACMA that reaches the Earth's surface
1:11 is called lava this molten lava
1:14 eventually cools to form new rock [Music]
1:19 [Music]
1:21 after more eruptions over time a mound
1:23 of rock builds up forming a cone-shaped
1:32 volcano volcanoes all have the same key
1:35 structure a collection of magma
1:37 underneath the volcano forms a hot
1:40 bubbling furnace called the magma chamber
1:46 the main vent allows this magma to escape
1:48 escape
1:51 and secondary vents a smaller outlets
1:54 the magma can travel through
1:56 the caved-in surface is called the crater
1:57 crater
2:00 it's created after an eruption blows the
2:05 top of the volcano eruptions occur when
2:07 pressure forces magma from the chamber
2:11 up the main vent towards the crater if
2:12 the ash and mud from a volcanic eruption
2:15 mix with rain water or snow it creates
2:18 fast-moving mud flows
2:21 the hot lava and overwhelming mud flows
2:29 however volcanoes are also essential for
2:35 scientists believe that volcanoes formed
2:38 Earth's first atmosphere by spewing
2:41 water vapor sulfur dioxide nitrogen and
2:45 carbon dioxide into the air and volcanic
2:47 eruptions continue to contribute to the
2:50 carbon cycle crucial to life by
2:52 releasing carbon dioxide
2:54 they can go through long periods of
2:57 being very active but they may also
3:00 become dormant not erupting for hundreds
3:03 or thousands of years and eventually
3:07 they can become extinct just leaving a
