-Volcanoes are the area of Earth's surface which magma and gases pass through.
-During an eruption, a molten rock, magma, is forced.
-When it flows out to the Earth's surface, it is called "Lava".
-Volcanoes can erupt on land or ocean.
-there are explosive and non-explosive eruptions.
Explosive
-Very destructive
-Ash, clouds of hot debris, gas shoots out during an explosive eruption.
-causes molten rock into many particles and hardens in the air.
-The ash can reach the upper atmosphere and stay on earth for a years.
-Can blast millions of tons of lava.
-Can make the mountain collapse.
Non-Explosive.
-Most common type of eruption.
-Lava flows calm
-Some places are covered with lava because of the Non-explosive eruptions.
-e.g. Northwest region of U.S
What is inside a Volcano?
-Magma Chamber= Body of a molten rock it is located deep underground.
-Magma rises from the magma chamber through a crack of earth`s crust.
-And then through the openings called the vents.
What is Magma made from?
-The composition of the magma affects how do they erupt.
-Silica, Water, and Gas.
-Water &magma = Explosive combination
-Silica-rich Magma traps Explosive gases.
-From volcanoes. lava erupts.
-Lava/ Pyroclastic material.
-Lava-liquid magma.
-Pyroclastic material=magma hardens when they are blasted.
-Non-explosive mostly magma only.
-Explosive mostly Pyroclastic material.
Types of Lava
-High Viscosity- stiff
-Low Viscosity- fluid
-Blocky lava&Pahoehoe= high viscosity -flow slowly.
-Aa & Pillow Lava=Low viscosity-flow quickly.
Types of Pyroclastic Material
-Volcanic bombs-large blobs of magma
-Lapilli- pebble like; little stones
-Volcanic Blocks-largest piece;
-Volcanic Ash-form when gases in stiff magma expand rapidly and gas bubbles explode in to tiny glasslike silvers.
Pyroclastic Flows
-Dangerous flow
-produced by enormous amounts of hot ash, dust,etc.
-temperature about 700 degrees.
-Rundown hill fast as hurricane. (200km/h)
Volcanic eruption cont.
-Volcanic eruption can affect the climate change.
-The ash and gases are ejected into the upper atmosphere.
-They also can block the sunlight and drop the temperature down.
SHEILD VOLCANO
-shield volcanoes are built of layers of lava.
-Which were released from the non explosive eruption.
-Over time, the layers of lava creates a volcano that has gently sloping sides.
CINDER CONE VOCANO
-made by pyroclastic material
-produced by non explosive eruption.
-usually small
-erupts for short time
-occur clusters (often)(sides of volcano)
-erode quickly.
COMPOSITE VOLCANOES
-sometimes called Stratovolcanoes.
-common type
-form from explosive eruption of pyroclatic material and lava.
-steep form the top
-some volcanoes.
Mount Fuji
Mount Rainier
Mount shasta
Mount St. Helens
-craters:funnel shapped pit near the top off the central vent off volcanoe.
-caldera:large, semicircular depression -forms when magma chamber is emty and cause ground above to sink.
-Lava Plateau: wide, flat landform- it is the result from repeated non-explosive eruption- spread over large area.
The formation of magma.
-How magma forms=why volcanoes erupt.
-Magma
-deeper regions of crust
-And upper most layer of the mantle where temperature and the pressure is very high.
-Change in pressure&temperature=magma form.
Pressure and temperature
-Upper mantle-made out of very hot, puttylike rock that flows slowly.
-Mantle is h0t enough to melt an Earth's surface.
-However, it remains puttylike magma because of the pressure.
-The weight of the rock above mantle pressure atoms of the mantle close together that rock cannot melt.
Magma formation in the Mantlee
-Common=decreased in pressure-magma formation.
-Once formed-magma is less dense than the surrounding rocks-so magma rises.
-locations of the volcanoes-how volcanoes form
-It lies directly above the tectonic plates boundaries.
-Plate boundaries that is surrounding Pacific ocean have many volcanoe-so it is called the ring of fire.
-Tectonic boundaries-collide,seperate, slide(tectonic plates.)
-Deep crack between the divergent boundaries are called "rift zone".
-Rises trough the rift(Magma)
-Causes new (ocenic) crust
Mid Ocean Ridge
-Magma flows under rift zone produces volcanoes and mountain chains Mid ocean ridge.
-Place where new crust forms.
-Earth is circled with mid-ociean ridge.
-Most volcanic activity on earth occurs in Mid ocean Ridge.
When tetonic Plates Collide
-Either one will go up and down
-Convergent boundary- collide
-When oceanic collides with continental, oceanic usually goes underneath.
-Subduction-movement of one tectonic plate underneath another.
-When the oceanic plate pases(slides) under continental plate, the temperature and the pressure increases.
-This causes the water in oceanic plate released and be mixed with mantle rock.
-Then it will lower the melting point.
-Hotspot:volcanically active area of earth's suface on the tectonic plate boundary.
-Some scientist think that hot sopt is directly on the mantle plums.(Rising magma)
-Volcanoes are classified in 3 ways.
:Extinct-did not erupt and no record of erupting in history. Also,probally not erupting again.
:Active-currently erupting/shows signals of erupting of the future.
:Dormant-currently erupting volcanoes. They might erupt again(high possibility)
-Most active volcanoes have small earthquakes.
-Rock to shift-earthquake.
-MOnitoring these quakes- best way to predict the eruption.
-Instrument:tiltmeter
1.it helps scientists detect small changes in the angle of the volcanoes slope.
2.Also use satellite(GPS)
3.Changes of slope- some may be signal for an eruption.
