Volcanic Eruptions
Describe the pyroclastic material and magma
What is Pyroclastic Material?
Volcanic Ash
Volcanic ash is formed during explosive volcanic eruptions. Vocanic ash that is less than 0.25 mm in diameter is called volcanic dust. Volcanic ash is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere.
Lapilli
Large pyroclastic particles that are less than 64 mm in diameter, are called lapilli, which is from a Latin word that means "little stones." Lapilli generally fall near the vent.
Volcanic Blocks
Large clots of lava may be thrown out of an erupting volcano while they are red-hot. As they spin through the air, they cool and develop a round or spindle shape. These pyroclastic parti les are called volcanic bombs. The largest pyroclastic materials, known as volcanic blocks, form from solid rock that is blasted from the vent.
Pyroclastic Material
What is lava flow?
Pahoehoe Lava
Pahoehoe is the least viscous type of mafic lava. It forms wrinkly volcanic rock when it cools. Pahoehoee actually means "ropy" in Hawaiian.
Aa Lava
Aa lava is more viscous than pahoehoe lava and forms sharp volcanic rocks when it cools.
Blocky Lava
Blocky lava is the most viscous type of mafic lava and forms chuncky volcanic rock when it cools. The high viscosity causes the cooled lava at the surface to break into large chunks.
Lava Flow
Types of Volcanoes
Belknap, Oregon Shield Volcanoes
Belknap, Oregon volcano is an example of a shield volcano.Volcanic cones that are broad at the base and have gently sloping sides are called shield volcanoes. Layers of hot, mafic lava flow out around the vent, harden, and slowly build up to form the cone. The Hawaiin islands form a chain of shield volcanoes that built up from the ocean floor at a hot spot.
Cerro Negro, Nicaragua Cinder Cones
The Cerro Negro, Nicaragua volcano is an example of a cinder cone.A cinder cone is a type of volcano that has a very steep slopes is a cinder cone. The slope angles of the cinder cones can be close to 40 degrees celcious, and the slopes are rarely more than a few hundred meters high. Cinder cones form from explosive eruptions and are made of pyroclastic material.
Mount Fuji,Composite Volcanoes
Mount Fuji, is an example of a composite volcano. A Composite volcanoes, also known as stratovolcanoes, commonly develop to form large volcanic mountains. During a quiet eruption, lava flows cover the sodes of the cone. Then, when an explosive eruptions occurs, largeee amounts of pyroclastic material are deposited around the vent.