"Is there basalt lava on Mars? What is basalt lava and how is it formed? Can you sleep on pillow basalt? What is the geological history of this area?"
Miles and Miles of Lava
Basalt rock up to 10,000 feet thick and consisting of more than 300 lava flows run for miles and miles under the semi-arid skies of eastern Washington. Some flows are over 90 feet deep. Beneath these massive layers is bedrock from earlier volcanic activity. On top of the granite bedrock we find sediment layers from glacial lakes, boulders and debris from glaciers, channels in the basalt and gravel bars left by giant floods, and fertile loess (fine dirt) blown in on the winds.
The material in basalt is from magma deep within the Earth's crust. Fully melted rock in magma that reaches the surface cools into granite. When the magma is from partially melted rock the lava becomes basalt. As the basalt flow cools the top and bottom layers separate into 5 to 7 sided sections called colonnades as seen in the picture above. Find out how these columns are formed on the Columbia Plateau Basalt page. When hot basalt lava flows into water Pillow Basalt is formed.
Our moon has large dark areas of basalt lava called "mares", Latin for seas. The early astronomers thought there might be oceans on the face of the moon. Mars has lava flows as well. In the NASA/JPL image at left the light and dark layers of a flow can be seen. It is part of a much larger area. Click on image for a detail view.
This is the NASA description of the full image:
"The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in 1998 confirmed that a vast region of Mars south of the Elysium volcanoes is covered by a relatively young lava surface that was very fluid when it erupted--so fluid that it ran more than a thousand kilometers (more than 600 miles) across a region known as the Elysium Basin and a channel named Marte Vallis."
"When it was forming, the lava flowed from the lower left, toward the center right, then curved to the left and flowed toward the top-center of the frame. The center of the lava flow in image 38804 has a wide, shallow channel bounded by steep, discontinuous walls--also known as levees. Such leveed channels are commonly the conduit through which some of the later stages of molten rock are transported along a lava flow. The margins of the lava flow are broken into plates--some of them several kilometers across. These plates were once part of a hard, rock crust that floated on molten lava. As the lava flowed down Marte Vallis, huge chunks of this crust broke off at the margins of the flow and floated a few kilometers away from where they had originated. Long after the lava had cooled and hardened, a distant meteorite impact splashed ejecta across the martian surface such that a field of small craters--known as secondary craters--formed on top of the lava flow shown here."
Some 200 million years ago the western edge of the North American continent was about 60 miles west of where Spokane is now. Fossils of ocean plants and animals have been found in the now-dry eastern Washington area.
How did this lush seacoast become a semi-arid desert?
The story continues on the Geological History page.
Here are some basic terms used in the tour. Find more geology terms in the Glossary.
- Volcanic rock caused by partial melting of the Earth's crust.
- The deepest part of a river or bay.
- Channeled Scabland
- Area in Washington state where huge floods made channels in a large, deep basalt flow. Named by J Harlan Bretz during the 1920's in various publications. See also Glacial Lake Missoula.
- Long winding channel cut through lava formations. A term primarily used in the northwestern United States.
- Lifting and removal of rock, dirt, sand and the like caused by wind, water, or glacial ice.
- Ice Age
- A period in Earth's history when much of the continents are covered with ice sheets and glaciers.
- Molten earth material (rock) that comes out of volcanoes or cracks in the Earth's crust.
- Fine dirt deposited by wind usually from arid or glaciated areas.
- Molten rock beneath the earth's surface. Magma is called "lava" when it erupts from a volcano.
Kids' Cosmos… Expanding Minds Beyond the Limits of the Universe
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