Volcano Notes 2013
1. volcano-an opening in Earth’s surface that erupts gases, ash, and lava.
2. Earth has more than 600 active volcanoes
3. volcanoes can be active, dormant (sleeping) or extinct (dead)
4. an active volcano is one that has erupted in recorded history
5. the world’s most active volcano is Kilauea on the Island of Hawaii. It has been erupting for over 25 years.
6. Iceland is known as the “Land of Fire and Ice”, because it is so far north and has several active volcanoes. Iceland is part of the Mid-Ocean Ridge.
7. Deep inside the Earth, heat and pressure melt rocks into a liquid called MAGMA.
8. Magma is less dense than the rock around it so it slowly “floats” to the Earth’s surface. Can take thousands of years to reach the surface.
10. magma that reaches the Earth’s surface is called lava.
11. vent-magma flows out of the Earth through an opening called a vent.
12. lava that cools and hardens on the Earth’s surface forms igneous rocks.
13. crater-the steep bowl-shaped area around a volcano’s vent
14. Volcanic mountains form when layers of lava, ash, and other material build up around these openings
15. Volcanoes are dangerous because of flowing lava, but also because of volcanic ash, dust, and poisonous gases. Ash can cause buildings to collapse and cause lung damage.
16. pyroclastic flow-volcanic ash, rocks, and other matter (but not lava) rushing down the side of a volcano
17. volcanoes often form where plates are moving apart (divergent) or are coming together (convergent)
18. Mid-Atlantic Ridge is a divergent plate boundary. When plates move apart, long, deep cracks called rifts are formed. Lava flows from the rift, cools quickly because of the cold seawater.
19. volcanoes also form at subduction zones caused by convergent boundaries. Convergent boundary volcanoes usually have more explosive eruptions.
20. hot spots are unusually hot areas of the crust where magma has melted into the crust, they are NOT near plate boundaries.
21. Hawaiian Islands and Yellowstone National Park are formed by volcanoes caused by a hot spot.
23. three types of volcanoes are shield, cinder cone, and composite.
24. shield volcanoes are built up from quiet eruptions of basaltic lava that spreads out in flat layers. Hawaiian Islands are shield volcanoes.
25. cinder cone volcanoes are formed by explosive eruptions throwing lava and rock high into the air. Rocks and solidified lava drop from the air, form the steep, loosely packed sides of the volcano.
26. composite volcanoes are a combination of quiet and explosive eruptions.
Nevado del Ruiz volcano in central Colombia, 130 km WNW of Bogota, is a broad, glacier covered volcano. A relatively small eruption in 1985 caused a devastating mud flow that killed almost 25,000 people in the town of Armero, marking one of the worst volcanic disasters in history. Sadly, this tragedy could have been easily avoided if clear warnings by volcanologists had been taken seriously.