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Volcanoes and Rift Valleys

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on 23 November 2014

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Transcript of Volcanoes and Rift Valleys

Volcanoes and Rift Valleys
by Ryan Shea
and Phoenyx Tosti
Rift valleys are splits in the Earth where two tectonic plates have diverged, pulling slowly apart until they suddenly release and split the Earth apart. This is a common example of convection.
Rift Valleys
Many factors cause rift valleys
Step 1
Convection currents in the mantle begin to push two plates apart.
Step 2
The currents slowly push away at the plates, making a divergent boundary.
Step 3
The crust pulls apart, creating a rift in the Earth that varies in size and length.
Step 4
The rift now may get stuck then unstuck, causing earthquakes. They may also spew magma through fissures in the sides.
All of these factors contribute to the creation of a rift valley.
Final Result
rift valley facts
Most famous
Rift Dangers
Rift valleys can get get stuck when pulled apart, and can cause devastating earthquakes.
Rift Dangers (continued)
Rifts also have a tendency to spew magma from fissures that appear down the middle or along the edges.
Underwater Rifts
Most rifts actually form beneath the ocean, because lots of subduction happens there. Underwater rifts are generally known as ridges and contribute to
sea-floor spreading

(see next).
Sea-floor Spreading
all in the name
The word "rift" is a Scandinavian word that was translated into Middle-English. It originally meant a break in a personal relationship.
The most famous rift valley known today is the East African Rift System, or E.A.R.S. It measures over 5,000 km long.
Magma erupts through ridge
Magma hardens and becomes part of oceanic crust
Oceanic crust gets subducted back into Earth at a deep-ocean trench
Subducted crust melts back into magma
The action of sea-floor spreading is a regenerative cycle.
Volcanoes
Volcanoes are powerful forces of nature. They're large tubes in the earth that form when magma rises from the mantle and escapes through the crust.
Eruptions
Lava is mostly caused to erupt by pressure when it is stored in the mantle. When it pushes up against a weakness or crack in the crust, the pressure is released, causing lava to erupt. Though a volcano can erupt by a magma chamber is filled and more magma joins it or when the magma is so buoyant it rises.

Eruption Pictures
What is lava made of?
Lava is mostly made up of crystals, volcanic glass, and bubbles that is melted. Lava is chemically made up of silicon, oxygen, aluminum, iron, magnesium, calcium, sodium, potassium, phosphorus, and titanium.
Why are they called volcanoes
Volcanoes got their name from the roman god Vulcan, who was said to have the power over volcanoes. The word originated from a small island in the Mediterranean called Vulcan, where it was believed that their city was the chimney for the forge of Vulcan (the Roman god of fire, volcanoes, blacksmithing, and the forge).
How many gallons of lava are erupted in one eruption?
There is no real average for the amount of lava expelled in one volcanic eruption. Some of the most destructive volcanoes have spewed materials of about 250 miles into the air (the Yellowstone Super Volcano about 640,000 years ago), others can explode with the energy of several hundred atomic bombs in just seconds (Thera between 1645-1500 BC), and some can wipe out entire cities (Mount Vesuvius, Pompeii and Herculaneum in 79).
What kind of rock do volcanoes create?
When a volcano erupts and the lava is expelled, there are three different types of lava; basalt, andesite, and rhyolite. When basalt lava cools, the rocks scoria and basalt are created, making a shield volcano. When andesite lava cools, different types of andesite rocks are formed, which in turn forms cone volcanoes. Rhyolite lava forms rhyolite rock, such as pumice, and form calderas, or, if there is enough gas in the rock, cone volcanoes.
What is the growth rate (on average) the growth rate and size of a volcano?
Most volcanoes grow bigger every time is erupts, the ash, lava, and rock gather around and on the volcano, adding to it growth. The growth and size of a volcano can vary greatly, the thickness can go from only a few meters to up to a kilometer, it is the same case for the length and diameter of the volcano.
lightning!!!!!!!!
Lighting can be caused by a volcano erupting, the gases and ash have different negative and positive charges, creating lighting storms inside the cloud.

Volcano/rift valley
Volcanoes and rift valleys might not be as different as you think! As it turns out, the E.A.R. system has caused some of Africa's highest mountains and most violent volcanoes, such as Mt. Kilimanjaro. When the two plates diverge, they push up mountains on either side. These mountains can serve as vents for inner mantle gasses and cause violent eruptions when released.
crossover!
volcanoes
rift valleys
sources

http://www.google.com/search?q=how+are+rift+valleys+formed&oq=how+are+rift+&aqs=chrome.1.69i57j0l5.9342j0j8&sourceid=chrome&es_sm=93&ie=UTF-8&gws_rd=ssl
http://education.nationalgeographic.com/education/encyclopedia/rift-valley/?ar_a=1
http://www.usgs.gov/faq/categories/10167/3527
http://www.britannica.com/EBchecked/topic/503375/rift-valley
http://geology.com/articles/east-africa-rift.shtml
http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=15855
End of presentation


http://www.google.com/search?q=how+are+rift+valleys+formed&oq=how+are+rift+&aqs=chrome.1.69i57j0l5.9342j0j8&sourceid=chrome&es_sm=93&ie=UTF-8&gws_rd=ssl
http://education.nationalgeographic.com/education/encyclopedia/rift-valley/?ar_a=1
http://www.usgs.gov/faq/categories/10167/3527
http://www.britannica.com/EBchecked/topic/503375/rift-valley
http://geology.com/articles/east-africa-rift.shtml
http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=15855
Full transcript