Flood Basalts
Flood basalts are yet another strange type of "volcano."
Some parts of the world are covered by thousands of square kilometers
of thick basalt lava flows - individual flows may be more than
50 meters thick, and individual flows extend for hundreds of kilometers.
The old idea was that these flows went whooshing over the countryside
at incredible velocities (e.g., like a flash flood). The new idea is
that these flows are emplaced more like flows, namely slow moving
with most of the great thickness being accomplished by injecting
lava into the interior of an initially thin flow. The most famous
US example of a flood basalt province is the Columbia River Basalt
province, covering most of SE Washington State and extending all
the way to the Pacific and into Oregon. The Deccan Traps of NW
India are much larger and the Siberian Traps are even larger than
that (but poorly understood). The Ontong Java plateau may be an
oceanic example of a flood basalt province.
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