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A flood basalt (or plateau basalt [1]) is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Many flood basalts have been attributed to the onset of a hotspot reaching the surface of the Earth via a mantle plume . [ 2 ]
The Columbia River Basalt Group (including the Steen and Picture Gorge basalts) extends over portions of four states. The Columbia River Basalt Group (CRBG) is the youngest, smallest and one of the best-preserved continental flood basalt provinces on Earth, covering over 210,000 km 2 (81,000 sq mi) mainly eastern Oregon and Washington, western Idaho, and part of northern Nevada. [1]
The cliffs come from the earlier Cenozoic Afton basalt flow; the magma that caused the maar explosion was also basalt. [1] Kilbourne Hole is a maar volcanic crater, located 30 miles (48 km) west of the Franklin Mountains of El Paso, Texas, in the Potrillo volcanic field of Doña Ana County, New Mexico. Another maar, Hunt's Hole, lies just two ...
Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of Venus, which cover ~80% of the surface, are basaltic; the lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars.
Basalt columns seen on Porto Santo Island, Portugal. Columnar jointing of volcanic rocks exists in many places on Earth. Perhaps the most famous basalt lava flow in the world is the Giant's Causeway in Northern Ireland, in which the vertical joints form polygonal columns and give the impression of having been artificially constructed.
Columnar jointing in Giant's Causeway in Northern Ireland Columnar jointing in the Alcantara Gorge, Sicily. Columnar jointing is a geological structure where sets of intersecting closely spaced fractures, referred to as joints, result in the formation of a regular array of polygonal prisms (basalt prisms), or columns.
Flood waters eroded the loess cover, creating large anastomizing channels that exposed bare basalt and creating butte-and-basin topography. The buttes range in height from 30 to 100 m (98 to 328 ft), while the rock basins range from 10 m (33 ft) in width up to the 11 km (7 mi) long and 30 m deep Rock Lake .
As mentioned above, the pre-rift stratigraphy of the central Gulf of Mexico basin, which now lies beneath nearly 20 kilometers of sediment deposited during the Jurassic through the Holocene, is made up primarily of extensional graben formations filled with "red beds," basalt flows, and diabase dikes and sills deposited and intruded during the ...