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Magma Vs. Lava
Magma consists of molten rock that flows from the Earth's interior into a volcano's vents. Magma's primary components include silicon, oxygen and iron. Lava can also flow from fissures in some shield volcanoes. Scientists call magma lava if a volcano erupts and sends the molten material flowing into the surrounding landscape.
Lava Flow Effects
As shield volcanoes erupt, lava builds up over time and forms gentle slopes around the volcano's central vents or group vents; some volcanoes have multiple vents. Shield volcanoes get their name from their resemblance to a warrior's shield when you view them from a distance. Some lava in a shield volcano is too vicious to flow significant distances. That lava helps form domes that surround the volcano's vent.
Changing the Landscape
When molten lava combined with cool ocean water, the black sand beaches in Hawaii formed. This type of landform creation occurs when lava flows into the sea or onto a shallow ocean floor. Cooling occurs so quickly that the lava shatters into pieces that cover the beaches. Southern Idaho, southeastern Washington and other locations contain broad plateaus that formed from lava flowing quietly from a shield volcano's fissures.
Famous Shield Volcanoes
Oregon's Newberry shield volcano has erupted thousands of times during the past 600,000 years. This volcano has a broad shield, and it contains at least 25 vents. Because it erupted so many times in the past, it's possible that future eruptions may occur. In addition to Mauna Loa, the Hawaiian Islands have Kilauea, a shield volcano that is also one of the most active volcanoes on the planet.
Distant Volcanic Activity
Shield volcanoes can also transform the landscape on other planets. Similar to shield volcanoes in Hawaii, Mars' Olympus Mons shield volcano towers 25 kilometers (16 miles) above the planet's surface and has a diameter of 624 kilometers (374 miles). Eruptions from Olympus Mons helped create several overlapping craters and radial features on the volcano's slopes that an orbiting satellite can see from space.