They are the most common type of volcanoes. Many cinder cones have a bowl-shaped crater at the summit. They are commonly found on the flanks of shield volcanoes, strato volcanoes, and calderas. Geologists have identified nearly 100 cinder cones on the flanks of Mauna Kea, a shield volcano located on the island of Hawaii. They are smaller and simpler than composite volcanoes. It forms when ash, cinders and bombs pile up around the vent to form a circular or oval cone. “Cinders are melted volcanic rock that cooled and formed pebble-sized pieces when it was thrown out into the air.”

“They are ejected from a single vent and accumulate around the vent when they fall back to earth.” “Cinder cones can occur alone or in small to large groups or fields.” “Most have a bowl-shaped crater at the summit.” “The longer the eruption, the higher the cone.” The shape of a cinder cone can be modified during its (short) life. “Cinder cones are built from lava fragments called cinders. The lava fragments are ejected from a single vent and accumulate around the vent when they fall back to earth.”

“A cinder cone or scoria cone is a steep conical hill of volcanic fragments that accumulate around and downwind from a volcanic vent. The rock fragments, often called cinders or scoria, 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. Cinder cones are made of pyroclastic material.”

Also called strato volcanoes Formed by alternating layers of lava and rock fragments Often have snow capped peaks Between eruptions, they seem extinct because they are very quiet Eruption is explosive Caused by viscous magma When the magma rises, it clogs the opening. This results in gas building up until it explodes

Can grow about 8,000 ft above bases Can grow very large but the sides weaken too much that the volcano collapses because of gravity Many located on the “Ring of Fire” Volcanoes form when an oceanic plate boundary and a continental plate boundary meet. The oceanic goes under the continental because it is denser. This is called subduction. Then hot magma rises and forms a volcano. They occur because the plates are moving. Underneath the crust, convection is circling around causing the plates to move and crash into each other.

Shield volcanoes are big and made up of fluid lava flows. They get their name because the sloping hills that surround them have a fan shaped pattern that looks like a shield. They have broad, sloping sides. Shield volcanoes are formed from the action of the gas or steam or water vapor with heat from the earth’s core. This melts rock turning it into magma. The pressure from the heat of the gas pushes the magma up until it explodes. Molten Magma shoots upward from under the ocean floor and breaks through the plates and forms a shield volcano.

Shield volcanoes could be made from hot spots under the surface. Shield volcanoes are built up of effusive eruptions. Shield volcanoes measure to about 3-4 miles in diameter. They measure up to 1,500-2,000 feet high.

Diagram of a Hawaiian eruption (key: 1. Ash plume 2. Lava fountain 3. Crater 4. Lava lake 5. Fumaroles 6. Lava flow 7. Layers of lava and ash 8. Stratum 9.Sill 10. Magma conduit 11. Magma chamber 12.Dike) Click for larger version

When a volcano explodes, houses, buildings, roads, and fields can get covered with ash. People will often evacuate their houses. If the ash is really heavy, it can make it hard, or impossible, to breathe.

The most destructive volcano is Mt. Tambora in Indonesia. It was an active composite volcano that occurred on April 5th It killed 12,000 people directly from the volcano, and 80,000 killed from starvation afterward. That is a total of 92,000 people killed!

Composite Volcanoes Mount St. Helens - Washington State Mount Rainier - Washington State Mount Vesuvius – Italy Mayon Volcano - Luzon Island, Philippines Mount Fuji – Japan Mount Cotopaxi – Ecuador Mount Shasta – California Mount Hood – Oregon Cinder Cone Volcanoes Cinder Cones and Scoria Cones California Cinder Cones Cerro Negro, Nicaragua Lava Butte, Oregon Newberry Caldera Vicinity, Oregon New Mexico Cinder Cones Paricutin, Mexico Portland Vicinity, Oregon Sunset Crater, Arizona Wizard Island, Crater Lake, Oregon Shield Volcanoes ·Kilauea (Hawaii) ·Mauna Loa (Hawaii) ·Etna (Sicily) ·Piton de la Fournaise (Reunion) ·Erta Ale (Ethiopia) ·Fernandina and all Galapagos volcanoes ·Nyamuragira (Congo) ·Karthala (Indian Ocean) ·Savai’i (Samoa) ·Aoba (Vanuatu)