Millions of years ago, lava flows poured molten rock over huge areas of the
world. These eruptions, known as basalt floods, hurled noxious gases fro
Earth's interior into the atmosphere. Toxic clouds ravaged the environment and
may have triggered mass extinction. The weathered remains of flood basalt can
still be seen around the world. but scientists do not yet understand the cause
of such vast eruptions. It is such a mystery that a basalt flood could burst
from the Earth tomorrow undetected.
Basalt floods smother whole regions of the Earth in molten rock. They are
released when immense volumes of magma apply pressure to the Earth's rigid crust
until it cracks around huge, violent fountains of lava. It can take over a
million years to exhaust the magma supply completely and end the flood.
The last major flood eruption covered Washington and Oregon 16 million years
ago and spread over 77,000 square miles.
It solidified as the Columbia River
Plateau and even after 16 million years of erosion, the flood basalt still cover
an area larger than the state of New York. The Deccan Plateau in India, which
erupted around 65 million years ago, is twice that size.
One possible cause of flood basalt is magma plumes. Magma forges a path from
chamber deep within the Earth's hot mantle and forces it way through the crust
n fissure that are sometimes over 50 miles long. There are no big bangs- gases
simply bubble through the highly fluid lava without blowing it apart. Each
fissure disgorges sheet of molten rock above ground that may smother up to
14,000 square miles of the surface.
Successive eruptions expel layer upon layer of basalt - in some places the
plateaus lie three miles thick. Flows of hot rock annihilate all life...