Ice Age Floods, Lake Missoula, Bonneville Flood and the Columbia River Basalts

[Intro Music]

The Pacific Northwest is famous for many
things.

Including huge floods.

Floods of lava that buried almost 40%
of Washington,

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

of scab lands.

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

North America?

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

the lowest point in the state.

The basalt bedrock here,

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

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

A flood of water from a giant lake in Utah

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

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

A giant lake in Montana

flowed to the cascades, got backed up
to here.

Each of these layers representing a
separate flood.

The Columbia River basalts,

the Bonneville flood,

and the Missoula floods.

Let's dig into together and learn,

about huge floods in the Pacific
Northwest.

[ Music Plays ]

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

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

The Columbia River basalt group,

a pile of lava rock more then 2 miles
thick,

is an exception to the global rule.

Basalt lavas usually erupt in ocean
basins,

but these low silica lavas flooded North
America from below.

Much like a boat with a leak.

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

and central Siberia.

In each case, very large volumes of fluid
basaltic magma

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

tens of thousands of square miles.

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

Washington and eastern Oregon,
starting 17.5 million years ago.

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

of a tectonic hot spot,

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

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

North American plates slowly moving over
the stationary hot spot.

These spectacular basalt lava eruptions,

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

each lava flood.

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

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

to the tower cliffs of the Oregon coast.

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

more then 3 miles of lava.

Sitting on top of a 17 million year old
landscape.

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

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

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

and the Columbia River Gorge,

or in the Grand Coulee,

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

By the Ice Age floods.

[ Music Plays ]

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

advancing and retreating in response to
global climate.

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

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

of ice, above present day Seattle.

With