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Flow banding is the result of a process of fractional crystallization which occurs by convection, if the crystals which are caught in the flow-banded margins are removed from the melt. The friction and viscosity of the magma causes phenocrysts and xenoliths within the magma or lava to slow down near the interface and become trapped in a viscous ...
[140] [145] The first date is from a lava flow remnant in Klastline Valley while the second date is from a Village Member basalt flow on the Tahltan River. [ 121 ] [ 145 ] Argon–argon dating of Village Member basalt about 2 km (1.2 mi) downstream from the mouth of the Tahltan River on the east bank of the Stikine River has yielded an age of 0 ...
Effusive basalt lava flows cool to either of two forms, ʻaʻā or pāhoehoe. [8] This type of lava flow builds shield volcanoes, which are, for example, numerous in Hawaii, [9] and is how the island was and currently is being formed.
Basalt (UK: / ˈ b æ s ɒ l t,-ɔː l t,-əl t /; [1] [2] US: / b ə ˈ s ɔː l t, ˈ b eɪ s ɔː l t /) [3] is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon.
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.
Eruptions of basalt magma typically produce elongate lava flows, as well as build cinder cones (piles of small frothy lava fragments or 'cinders') around volcanic vents. [4] Basaltic volcanism in the Lassen volcanic area occurs mainly along chains of vents aligned in a north or northwest direction, parallel to regional faults.
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 ]
At least three lava flows are clearly visible in the rugged cliffs. The Cheakamus Valley basalts are a sequence of basaltic lava flows along the Cheakamus River in southwestern British Columbia, Canada. They are part of the Garibaldi section of the Cascade Volcanic Arc and were produced during an episode of volcanic eruptions from an unknown ...