WEBVTT

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[Intro Music]

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The Pacific Northwest is famous for many 
things.

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Including huge floods.

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Floods of lava that buried almost 40%
of Washington,

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and floods of Ice Age water that
created more than 2,000 square miles

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of scab lands.

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What are the odds that such rare events
both happened here in this corner of

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North America?

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We're just south of Lewiston Idaho at the
mouth of Hills Canyon,

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the lowest point in the state.

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The basalt bedrock here,

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the floods of lava, came out of deep 
cracks that formed in response to a heat

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source that's now, in the state of
Wyoming.

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A flood of water from a giant lake in Utah

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came all the way through Southern Idaho,
through Hills Canyon,

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dropped rocks here, and the water made it
to the Pacific Ocean.

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A giant lake in Montana

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flowed to the cascades, got backed up
to here.

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Each of these layers representing a 
separate flood.

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The Columbia River basalts,

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the Bonneville flood,

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and the Missoula floods.

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Let's dig into together and learn,

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about huge floods in the Pacific 
Northwest.

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[ Music Plays ]

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The Ice Age floods have helped exposed
and incredible pile of lavas

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from erupting volcanoes that are not
related to our famous cascade volcanoes.

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The Columbia River basalt group,

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a pile of lava rock more then 2 miles
thick,

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is an exception to the global rule.

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Basalt lavas usually erupt in ocean 
basins,

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but these low silica lavas flooded North
America from below.

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Much like a boat with a leak.

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They're similar flood in central India,
southern Brazil, southern Africa,

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and central Siberia.

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In each case, very large volumes of fluid
basaltic magma

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erupted rapidly from cracks and continents
to form sheets of lava rock covering

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tens of thousands of square miles.

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The deep crack called fissures cracked
the North American crust in south eastern

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Washington and eastern Oregon,
starting 17.5 million years ago.

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Today many geologist agree that the 
fissures are directly related to the birth

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of a tectonic hot spot,

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beneath the out south-eastern Oregon
17.5 million years ago,

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and now located underneath Yellowstone 
National Park in Wyoming due to the

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North American plates slowly moving over
the stationary hot spot.

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These spectacular basalt lava eruptions,

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more than 300 distinct events punctuated
by thousands of years of quiet between

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each lava flood.

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Flooded and buried, the rugged inland
landscape of the Pacific Northwest.

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Many of the biggest lava flows made it
from their fissures in Idaho all the way

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to the tower cliffs of the Oregon coast.

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At Pasco Washington the stack of Columbia
River basalt lava flows is 1,600 ft. thick

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more then 3 miles of lava.

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Sitting on top of a 17 million year old
landscape.

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There isn't one visage to see all the
lava flows, how could you?

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To truly grasp the scale of the lava stack
one has to visit scattered canyons that

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expose a dozen flows at a time, like
in the Yakama River Canyon,

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and the Columbia River Gorge,

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or in the Grand Coulee,

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which was carved just thousands of years
ago, not millions.

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By the Ice Age floods.

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[ Music Plays ]

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During the Ice Age, a thick ice sheet
covered much of North America,

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advancing and retreating in response to
global climate.

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In Washington, Canadian ice crossed the
border in different places.

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West of the cascade range, the Puget Lobe
filled the Puget Lowland with 3,000 ft.

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of ice, above present day Seattle.

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With