Science: Chapter 3, section 1 Flashcards
where are the Earth’s volcanic regions and why are they found there?
VOlcanoes form along the boundaries of the Earth’s plates. They usually occur along diverging plate boundaries, such as the mid-ocean ridge, or in subduction zones around the edges of oceans. They occur here because the crust is weak and fractured and this allows magma to reach the surface.
what is a volcano
a weak spot in the Earth’s crust where molten material (magma) comes to the surface
what is magma
a molten mix or rock,-forming substances, gases and water from the mantle.
what is lava
magma that reaches the Earth’s surface. When it cools, it forms solid rock.
what type of force is a volcano and what does it do to the Earth’s surface
it is a constructive force that adds new rock to existing land and forms new islands
how many active volcanoes are on Earth
appx 600 on land and many more beneath the sea
what is the Ring of Fire
an active volcanic belt formed by many volcanoes that rim the Pacific Ocean
along the mid-ocean ridge, lava pours out of cracks in the ocean floor. Where do the volcanoes of the mid-ocean ridge rise above the Earth’s surface
only a few places- Iceland and the Azores Islands in the Atlantic Ocean
what is an island arc and give some examples
volcanoes create these string of islands when two oceanic plates collide and the older plate goes under the other plate. the older plate melts and forms magma. The magma seeps upward through the cracks in the crust. It breaks through the ocean floor and creates volcanoes. The resulting volcanoes form a string of islands called the island arc. The curve is just like the curve of the under-lying deep ocean trench.
Major island arcs include Japan, New Zealand, Indonesia, the Philippines, the Aleutians and the Caribbean Islands,
how does oceanic crust eventually become magma
when two oceanic plates collide, the older plate dives under the other plate and creates a deep ocean trench. the lower plate sinks beneath the trench into the asthenosphere and begins to melt- this forms magma.
what is a hot spot. give an example
an area where magma forms deep within the mantle that melts through the crust like a blow torch. They often lie in the middle of continental or oceanic plates- far from plate boundaries. They do not result from subduction.
The Hawaiian islands and Yellowstone National Park formed over a hot spot
how does subduction cause volcano formation. give an example
when the edges of a continental plate and an oceanic plate collide that can also produce volcanoes. The Andes Mountains in south America and the volcanoes of the Pacific northwest.
