Volcanic eruptions
Describe pyroclastic material and lava flows
Three types of magma.
Pahoehoe , Aa, blocky lava
Pahoehoe
Is the least vicious type of mafic lava. When it cools fast, a crust forms at the surface of the flow. If the lava continues to flow after the crust is formed, the crust will wrinkle and it will form a volcanic rock known as pahoehoe. The pahoehoe rock is formed from hot , fluid lava.
Aa lava
The crust deforms fast or it grows too thick to form wrinkles, the surface breaks into jagged chunks that forms Aa. It forms lava that has the same composition as pahoehoe.
Blocky lava
It has a higher silica than Aa lava. Which it makes blocky lava more viscous. The high viscosity causes the cooled lava at the surface too break into large chunks, while hot lava underneath continues too flow.
Types of pyroclastics
Lapilli
Large pyroclastic particles that are less than 64 mm in diameters are called "lapilli". Which is a Latin word that means "little stones".
Volcanic bombs
Large pieces of lava that may be thrown out from an erupting volcanoe while they are red hot. While their spinning through the air , it cools down and it developes a a round or spindle shape.
Volcanic ash/ volcanic dust
Scientist clasiffy pyroclastic materials according to the size of the particles, for example, Some pyroclastic particles that are less than 2mm in diameter, are known as volcanic ash. It mostly settles on the land that surrounds the volcanoe. Some of the smallest dust particles travel into earths upper atmosphere.
Volcanic bombs
Types of Volcanoes
Shield volcanoes
A shield volcanoe has a gentle slope along the side and It covers a wide area that generally forms a quiet eruption. Layers of hot mafic lava flows out from the vent it hardens, then it slowly build up the cone.
Cinder cones
A cinder cone is a type of volcanoe that has very steep slopes. The angle of it can be as close to 40 degrees and the slopes are rarely more than 100 meters high. Cinder cones form explosive eruptions and is made up of pyroclastic material.
Composite volcanoes
A composite volcanoe is made up of pyroclastic material and alternating layers of lava flows. When a quie eruption occurs, lava flows cover the sides of the cone. When a violent eruption occurs, a large amount of pyroclastic material gets deposited around the vent. Composite volcanoes are also know as stratovolcanoes.