Volcanoes
What is a volcano?: A volcano is an opening or rupture, in the Earth's surface. This allows lava, hot magma, ash, and gases to escape from the top or sides.
What is a vent?: Vents are flat linear cracks through which lava emerges. These vents are found at the top or at the sides of volcanoes.
Where do most volcanic eruptions occur?: In the Ring of Fire around the Pacific Ocean
What is a vent?: Vents are flat linear cracks through which lava emerges. These vents are found at the top or at the sides of volcanoes.
Where do most volcanic eruptions occur?: In the Ring of Fire around the Pacific Ocean
There are three types of volcanoes:
Shield Volcanoes
A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low height, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes. This results in the steady growth of layers of lava, building up the shield volcano's distinctive form.
Composite Volcanoes
A composite volcano, also known as a strato cone volcano, is very tall, and is built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, composite volcanoes are characterized by a steep profile and periodic, explosive eruptions. The lava that flows from strato volcanoes typically cools and hardens before spreading.
Cinder Cone Volcanoes
A cinder cone is a extremely steep hill of volcanic fragments that accumulate downward from a volcanic vent. The rock fragments, often called cinders, are glassy and contain numerous gas bubbles "frozen" into place as magma exploded into the air and then cooled quickly. Cinder cones range in size from tens to hundreds of meters tall. Many cinder cones have a bowl-shaped crater at the summit. Lava flows are usually erupted from here.
Active?, Dormant?, or Extinct?: Volcanoes can be one of these three things, dormant, active, or extinct. There is no real areement among volcanologists on how to define an "active" volcano. The lifespan of a volcano can vary from months to several million years. Extinct volcanoes are those that scientists consider unlikely to erupt again, because the volcano no longer has a lava supply, these volcanoes have to be dormant for at least 200 million years to be classified as extinct. It is difficult to distinguish an extinct volcano from a dormant one. Volcanoes are often considered to be extinct if there are no written records of its activity. Nevertheless, volcanoes may remain dormant for a long period of time.
Active?, Dormant?, or Extinct?: Volcanoes can be one of these three things, dormant, active, or extinct. There is no real areement among volcanologists on how to define an "active" volcano. The lifespan of a volcano can vary from months to several million years. Extinct volcanoes are those that scientists consider unlikely to erupt again, because the volcano no longer has a lava supply, these volcanoes have to be dormant for at least 200 million years to be classified as extinct. It is difficult to distinguish an extinct volcano from a dormant one. Volcanoes are often considered to be extinct if there are no written records of its activity. Nevertheless, volcanoes may remain dormant for a long period of time.