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[Intro Music]

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The Pacific Northwest is famous for many [br]things.

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Including huge floods.

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Floods of lava that buried almost 40%[br]of Washington,

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and floods of Ice Age water that[br]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[br]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[br]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 [br]cracks that formed in response to a heat

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source that's now, in the state of[br]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,[br]through Hills Canyon,

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

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A giant lake in Montana

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flowed to the cascades, got backed up[br]to here.

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Each of these layers representing a [br]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 [br]Northwest.

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[ Music Plays ]

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

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from erupting volcanoes that are not[br]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[br]thick,

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is an exception to the global rule.

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Basalt lavas usually erupt in ocean [br]basins,

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but these low silica lavas flooded North[br]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,[br]southern Brazil, southern Africa,

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and central Siberia.

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In each case, very large volumes of fluid[br]basaltic magma

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erupted rapidly from cracks and continents[br]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[br]the North American crust in south eastern

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Washington and eastern Oregon,[br]starting 17.5 million years ago.

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Today many geologist agree that the [br]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[br]17.5 million years ago,

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

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North American plates slowly moving over[br]the stationary hot spot.

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These spectacular basalt lava eruptions,

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

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each lava flood.

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

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Many of the biggest lava flows made it[br]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[br]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[br]landscape.

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

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

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expose a dozen flows at a time, like[br]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[br]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[br]covered much of North America,

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advancing and retreating in response to[br]global climate.

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

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

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of ice, above present day Seattle.

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With