Volcanoes #1

Frage	Antworten
What is magma?	It is molten rock.
Where is magma located?	Under the surface of the earth.
Where is a magma chamber located?	Far beneath the surface of the earth where an oceanic plate is driven down into the mantle by a continental plate.
What does an oceanic plate do when it descends into the mantle?	It melts. Some ocean water gets trapped and is turned into steam by the intense heat.
The molten rock and gas collect in a ______ ________ until it can escape to the surface.	magma chamber
How are stratovolcanoes built?	By many alternating eruptions of lava and ash.
What does the magma below stratovolcanoes do?	It experts a lot of pressure and pushes its way through small cracks in the crust and finally reaches the surface.
What is a dike?	It is an intrusion of magma that cuts through layers of already existing rock.
What is lava?	It is when magma reaches the surface of the Earth.
What does lava leaving the side vent cause?	It causes the volcano to add a layer of lava and ash. Also, with each eruption building the volcano higher and wider.
What is a conduit?	It is a main tube or pathway for the magma to reach the surface.
What is an example of a cooled and hardened conduit?	Devil´s Tower in Wyoming.
How was Devil´s Tower formed?	It was formed when the magma in the conduit cooled and hardened into a very hard lava rock called basalt.
What was the Devil´s Tower made of?	It was made of softer volcanic materials probably ash and pumice that slowly eroded away leaving only the conduit standing.
What is a crater?	It is a bowl shaped opening. It is the also the steep sided walls made of hardened lava that surround the main vent.
Where is a crater located?	It is located at the top of a volcano.
Where can lava flow?	It can flow from the main vent, but not all volcanoes eject large amounts of lava. Some volcanoes explode molten rock and huge amounts of gas from the main vent.
Are volcanoes always erupting? Why?	No. The crater may be a bubbling caldron of lava without enough pressure to erupt.
How are the steep walls of a volcanic crater are produced?	By many eruptions ejecting very liquid lava. It lands on the crater walls making them higher and higher.
How hot is the lava in the min vent?	1800 degrees F.
What does the lava on the top of the main vent do?	It cools and hardens because the air that is in contact with it is much cooler.
What does the lava do after is cools?	It gets dragged back down under the surface and gets remelted.
What is tuff?	When stratovolcanoes are built, some of the lava and ash lands and stays on the volcano building it higher and higher with each eruption. The ash hardens into a rock tat is called tuff.

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