SHIELD
VOLCANOES
created by R. Mason Geol 1100 The Richard Stockton College of NJ
Shield volcanoes are a type of volcano given their name for their broad gently sloping profile which looks like a warrior's shield. They are composed of thousands of fluid lava flows that spread great distances, sometimes greater than 50 kilometers. The tallest volcano in the world is a shield volcano. Mauna Kea Volcano rises 13,798 feet above sea level but extends about 19,700 feet to the ocean floor, for a grand total of 33,500 feet above sea level, dwarfing the world's tallest mountain, Everest, by over 4,000 feet! Mauna Loa, located on the island of Hawaii, has a height of 28,000 ft, but it has a much greater volume than Mauna Kea. It holds an estimated 80,000 km3 of basalt!
Shield volcanoes are also some of the world's most active. Kilauea, also on the island of Hawaii, began erupting in January of 1983, and still shows no signs of abating.
The photo to the left shows the eruption of Kilauea. Notice the pahoehoe and aa lava flows typical of shield volcano eruptions. There is little pyroclastic debris. This is why shield volcanoes are said to have silent eruptions. |
Shield volcanoes can erupt through central vents, or the lava can pour out from long fissures, creating broad plateaus. One example is the Columbia River Plateau in the states of Washing- ton and Oregon, whose lava flows can measure more than a mile deep. |
One reason why the lava from shield volcanoes can cover such great distances before cooling is due to lava tubes. Lava tubes are formed during long lived eruptions when the surface of a lava flow begins to stick to the sides of its channel. When it sticks it cools. Over a period of time the entire surface of the lava flow will be cooled. The crust will now insulate the lava inside of it, allowing it to flow for several more miles. |
Some interesting shield volcano facts?