Volcanoes
Volcanoes are areas of earths surface through which magma and volcanic gases pass. During an eruption, molten rock or magma, is forced through the earth surface. There are two types of eruptions explosive and non-explosive. Non-explosive eruptions are the most common type of eruption and can produce large flows of lava. Lava is liquid magma that flows out of a vent. The other type of eruption is explosive. Instead of producing lava flows, explosive eruptions cause molten rock to be blown into dust size particles called ash. Pyroclastic material forms when magma is blasted into the air and hardens. Pyroclastic flow is a dangerous type of volcanic flow and is produced when large amounts of hot ash, dust, and gases are ejected from a volcano. A magma chamber is a body of molten rock underground that feeds a volcano. A caldera can appear when a magma chamber partially empties and the magma chambers roof collapses. Magma rises through cracks in the earths surface called vents. The key to knowing whether a eruption will be explosive or non-explosive is the water and gas content in the water. There are four types of lava Aa, Pahoehoe, pillow lava, and blocky lava. The four types of pyroclastic materials are volcanic bombs, lapilli, volcanic ash, and volcanic bombs. There are three types of volcanoes. Shield, cinder cone, and composite are the three types of volcanoes. Shield volcanoes are built of layers of lava released from repeated nonexplosive eruptions. Their sides are not very steep bu they can be enormous. Cinder cone volcanoes are made of pyroclastic flow and form steep slopes. Cinder cone volcanoes are small and usually have a small eruption time but can have very explosive eruptions. They also appear clusters and erode quickly because the pyroclastic material is not cemented together. Composite volcanoes, or strata volcanoes, are one of the most common volcanoes. Their eruptions usually consist of pyroclastic material followed by quieter flows of lava. A crater is a funnel shaped pit near the central vent of a volcano. Hot spots are volcanically active places on the earth far from any plate boundaries. (Holt Science and Technology Earth Science) (file://localhost/Users/tholt19/Desktop/imgres-14.jpeg) ( file://localhost/Users/tholt19/Desktop/imgres-13.jpeg) ( file://localhost/Users/tholt19/Desktop/url-11.jpeg)