Volcanoes. Volcano. A volcano is a hole in the Earth’s crust where magma flows out. Volcanoes are created through subduction (where one plate slides under another). Volcanic Eruptions. Volcanoes will erupt for two reasons:
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Volcano A volcano is a hole in the Earth’s crust where magma flows out. Volcanoes are created through subduction (where one plate slides under another).
Volcanic Eruptions Volcanoes will erupt for two reasons: • The magma deep under the crust is less dense than the surrounding rock causing it to rise; • As the magma approaches the surface of the Earth, the gas that is in the magma will come bubbling out because the pressure surrounding the magma will decrease nearer the surface. Still confused? An example…
Volcanic Eruptions “Have you ever had a can of soda pop explode all over the room? This "eruption" of pop is caused by the same scientific principle that causes a volcano to erupt violently. When you open the pop can the pressure is released so quickly that the gas that is dissolved in the pop comes rushing out along with some of the pop.” http://volcano.oregonstate.edu/vwdocs/vwlessons/lessons/Cones/Cones2.html
Can you predict a volcanic eruption? • To an extent… here are some warning signs: • Earthquakes around the volcano • A bulge (swelling) on the volcano indicates magma is building up • Emission of gases, such as carbon dioxide • Increase in water temperatures around the volcano
Are volcanoes being monitored? Yes! There are 16 ‘Decade Volcanoes’, which are volcanoes designated likely to have violent eruptions again, with added concern because of their close proximity to large populations. They are currently being monitored in the event of a potential eruption. Some notable ones are: Mount Etna (Italy), Mount Rainier (Washington, USA), Taal Volcano (Philippines), and Mount Vesuvius (Italy)
Submarine Volcano Submarine volcanoes form the same way normal volcanoes do, but the process of subduction is happening underwater. They can also form over “hot spots”, where magma flows out from the seabed.
Pacific Ring of Fire Hot Spots are currently forming the Hawaiian Islands. The Hawaiian Islands are part of the Pacific Ring of Fire, which is a zone of frequent earthquakes and volcanic eruptions.
Hawaiian Volcanoes • The Hawaiian Islands are a chain of volcanoes that formed over 70 million years ago • Kilauea is the most active volcano, and has been ‘erupting’ continuously since 1983! • The lava is not very viscous, meaning it flows very easily Video: Kilauea Eruptions 3:02 minutes
Magma Magma is molten rock that comes from the mantle – the inside of a volcano.
Lava Lava is the magma that comes out of the volcano and ‘pours’ down the sides. Lava flows tend to move slowly, but destroy everything in their path.
Pyroclastic Flows Pyroclastic flows are a high-density mixture of hot, dry rock fragments and gases that move at high speeds.
Lahar Lahars are a mixture of hot or cold rock fragments and water that move down the side of a volcano.
Effects of Volcanoes • Wind and debris • Ash and cinders • Heating water • Gas and steam • Lava flows • Tsunamis
Volcanic Activity Active Volcanoes Volcanoes that are currently erupting or showing signs of unrest. Dormant Volcanoes Volcanoes that are not currently active, but could erupt again. Extinct Volcanoes Volcanoes that are unlikely to erupt again.
Volcanoes in Canada The only active/dormant volcanoes in Canada now are found in Northwestern B.C. and the Yukon Territory.
Eruption • Located east of Naples, Italy • Major eruption occurred in 79 AD • Preserved the cities of Pompeii and Herculaneum
Eruption • Located in Washington State, USA • Major eruption on May 18, 1980 • The eruption was the deadliest and most economically destructive volcanic event in the history of the United States
Play National Geographic: The Mount St. Helens Eruption Video 10:15 minutes
Mount St. Helens Mount St. Helen’s Volcano Camera: http://www.fs.fed.us/gpnf/volcanocams/msh/views/java-classic.php
Fin! Any questions?