R.E volcanoes, earthquakes Flashcards
Where are volcanoes found?
at destructive and constructive plate margins
How does a volcano happen at a destructive margin?
oceanic plate goes into the mantle,melted /destroyed
pool of magma forms, which rises through cracks erupts onto surface.
what are the cracks in the earth called?
vents
What is magma called once it reaches the surface?
lava
How do volcanoes at constructive margins happen?
Magma rises through gap of plates moving apart
Volcanoes also form on mantle what is this called?
Hotspot e.g Hawaii
Name 3 types of volcanoes?
shield, composite and dome
What are the layers in a composite volcano?
ash and thick lava (into a steep volcano)
Give example of composite volcano?
Mount Fuji ,Japan
How is a shield volcano formed?
Only runny lava, flows quickly, spreads wide forming a low flat volcano.
Give example of a shield volcano?
Mauna Loa, Hawaiian Islands
How is a dome volcano formed?
Only thick lava, flows slowly ,hardens quickly forming steep sides.
Names ways scientists predict volcanic eruptions?
tiny earthquakes, escaping gas, shape changes in the earth (bulges in land where magma has built up.
Where are super volcanoes formed?
at destructive plate margins and hotspots
How are super volcanoes formed?
magma rises up to form a magma basin below the surface, causing a circular bulge kms wide,
bulge cracks, lava escapes through vents, causing earthquakes, gigantic plumes of ash and rock,
lava empties bulge collapses leaving a big crater ( caldera)
Characteristic of a super volcano?
Flat, cover a large area, have a caldera ( regular volcanos have a crater)
Give example of a caldera filled with water?
Lake Toba
Name the last supervolcano to have erupted?
Lake Toba 74,000 years ago
Consequences of a super volcano?
thousands of cubic kms of rock, ash and lava.
cloud of thick super-heated gas and ash flow at high-speed across 10s of miles.
ash will block out daylight could trigger a mini ice age
ash will settle over 100s sq kms burying everything.
When does an earthquake happen?
plates can get stuck, when they become unstuck it causes an earthquake
what type of plate margins do earthquakes happen at?
All 3
What are destructive type earthquakes?
tension builds when 1 plate gets stuck as its moving past the other into the mantle
What are constructive type earthquakes?
tension builds along cracks in the plates as they move apart
What are conservative type earthquakes?
plates are grinding past each other and get stuck
