Tag Archives: Missoula Floods

A Perspective of Time

Argillite Boulder – Rattlesnake Mountain, Washington

This image depicts an interesting perspective of time.  The rock in the foreground was deposited here on Rattlesnake Mountain around 15,000 years ago.  The Rattlesnake Mountain and the Horse Heaven Hills in the background were created as part of the Yakima Fold formation about 1.5 million years ago.  The bedrock of this area is basalt from basalt flows through eastern Washington from 6-15 million years ago. The argillite boulder in the foreground is metamorphic rock from western Montana formed 1.5 billion years ago.

So here I was, sitting on a rock created before life on earth existed, brought here by a humongous flood around 15 thousand years ago, deposited on mountains uplifted 1.5 million years ago, created by a series of gigantic lava flows about 2 miles thick 6-15 million years ago.  And I think I am old at 67 years. As many of my Whizzy friends would say, “It’s a thinker.”

Granite Erratic

Granite Erratic – Rattlesnake Mountain, Washington

The Missoula Floods carried large icebergs from the glaciers that dammed Lake Missoula or from the Okanagan lobe glacier that dammed Lake Columbia along with them as they made their way to the Pacific.  As the icebergs melted or became “stranded” against ridges that formed Lake Lewis, they dropped the rocks that the glaciers picked up as they scoured their paths southward.  Granite is present in Montana as well as northern Washington.  But it is not present in central Washington.  The origin of this single granite erratic on Rattlesnake Mountain is therefore not definite. It could have come from either Montana or northern Washington.

This chunk of granite is approximately 6′ in length.  It is located at about 800 feet elevation (my estimate).

Drumheller Channels Overlook

Drumheller Channels Overlook

It is hard to comprehend how enormous the Missoula Ice Age Floods were.  The edge of the bluff in the top left hand corner is approximately 200 feet high.  The water level during the Missoula Floods was about 200 feet above the top of the mesa.  The distance across the Drumheller Channels was 8-11 miles wide.  The water is estimated to have moved through here at 50+ miles/hour.  The landscape left behind is amazing.  My mind wanders about contemplating what it must have been like.

This image was taken at the overlook off the main road running through the reserve.

Missoula Floods: Rattlesnake Ridge – Here Comes the Rain

Rattlesnake Ridge and Pasco Basin from Saddle Mountain, Washington

This image was taken from the top of Saddle Mountain looking southwest toward Rattlesnake Ridge.  During the Missoula Floods, the water level of Lake Lewis between these two ridges was about 600 feet above the current basin floor.

As I was photographing on top of the mountain, I felt a cold wind pick up.  The skies turned dark and I could see the rain coming toward me.  I decided it was a good time to pack up my gear and head down the steep gravel/dirt road before it turned to mud.  It was the end of a good day and a great trip driving around the Pasco basin exploring for traces of the Ice Age floods.

Missoula Floods: Sentinel Gap 2

Sentinel Gap, Washington

This image was taken north of Sentinel Gap, looking south.  The Columbia River is barely visible in the center of the photo.  During the Ice Age Missoula Floods, Crab Creek thundered through here joining the Columbia River.  This was the western path for the waters rushing through Drumheller Channels as it was diverted by the Saddle Mountains.  The small rocks in the foreground are likely to have been carried by the rush of water as it carved out the scablands through the Drumheller Channels.

Missoula Floods: Sentinel Gap

Sentinel Gap, Washington

This image was taken looking north through Sentinel Gap.  This gap cuts through the Saddle Mountains which separate the Pasco and Othello basins in Eastern Washington.  The Columbia River runs through this gap on its way to the Oregon/Washington border.  At the time of the Missoula Floods, the water level going through the gap reached the top of the left ridge, flowing into Lake Lewis which covered the Pasco basin.

The erratics in the foreground most likely are from the gap, carved away by the raging wall of water that flowed through it.

Missoula Floods: How Did This Get Here?

Granite Erratic in Pasco Basin, Washington

The Central Washington Basin is covered with layers of basalt, totaling as much as 2 miles thick, created by huge lava flows 8-15 million years ago.  The nearest source of granite rock is several hundred miles away.  This photo was taken near the Hanford site north of Richland.  The granite rock was about 1/4 mile from the road.  My lens combination was 560mm.  For reference, the actual height of the rock (above ground) is about 12 feet.  It is a big granite rock.  How did it get here???

The current theory is that it was brought here as part of the ice dam that broke loose during one of the Missoula floods around 15,000 years ago.  As the ice melted, embedded rocks were released.  The Pasco basin and its surround hills have many such erratics.

Missoula Floods: Facing Drumheller Channels

Drumheller Channels in Distance from Top of Saddle Mountain

This image was taken from the top of Saddle Mountain (~1,300 ft elevation) looking north east over the Othello basin toward the Drumheller Channels.  Imagine a wall of water 200 – 300 feet high racing over an 8-11 mile stretch over the Drumheller Channels at over 60 miles per hour.  This was the amount of water that was released (multiple times) when the Lake Missoula glacier dam broke releasing the water over the Eastern Washington basin.  Saddle Mountain broke the onslaught of water.  Some flowed west through the Crab Creek Coulee to the Columbia River and Sentinal Gap.  The remainder rushed around the eastern edge of the Mountain and into the Pasco Basin and Lake Lewis.