Volcano - created from Mind Map

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Is a conical or dome shaped landform built by the emission of lava and its contained gases from a constricted vent on the earth's surface

Begins when a fissure develops in the crust and magma forcefully move tpwards the surface through a vent

The form (shape and size) is determined by the composition of magma.

Magma is completely or partly molten material orginatinting from earth's interior.

When it reaches the surface-> Lava

Lava is produced from magma and has generally lost materials that escape as gas

A fragment of rock during a volcanic eruption is known as Pyroclast.

These ejected rocks vary from very fine dust to sand sized volcanic ash.

Typically dark, tempestous omni-loking masses. At a height at which the denisty of material in coloumn is equal to the atm, coloumn will spread out laterally to form mushroom shaped clouds.

As the magma approaches the surface, rapid decompression causes the gases to expand and produce violent upward thrust of a dense mixture of hot gas and tephra.

This is mixture rises rapidly in the cooler air above the vent to form the coloumn and may reach as high as 45km.

Magma contains varying amount of disolved gases held in molten rock by confining pressure

They make up 1-6% of the weight of magma and they contribute significantly to the gases that make up the earth's atmosphere

Hot blasts of high pressure gases from beneath that expands the cracks and develop passageway.

2 types: Basalt (major) and Andesite.

Depending on the type of lava flow, the speed and temperarure of the lava differs

80% of world's distribution

5%

Solidify at the earth surface

crystalling at depth

Higher the temp, lesser viscous, flow more easily

more gases, more buoyant and fuid. so higher the temperature, more gases present and hence less viscous

more silica, more vscous as it has close jointing and makes it flow slow and difficult for gas to escape.

Low viscosity magma with low dissolved gases amd low silica content but at higher temperature.

Effusive eruption (without explosion) as magma is more fluid and is quiet

Results from the partial melting of the ocean crust at the subduction zone at convergent boundaries

More viscous, flows slowly and travels less distance

Intermediate rock (andesite)

High silica content ]

Explosive eruption due to the presence of more viscours and high gas content.

More gas can dissolve As the gas bubble rises, less pressure and the bubbles expand and hence explode

Fine materials transported by high atm winds. Debirs eventually settles back onto the earth surface by gravity

Mixture of gas and pyroclastic debris that is so dense that it hugs the ground as it flows rapidly into low areas. Can travel up to 100km fromt he source at speeds of 700km/hr

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