What caused the 'Great Spokane Flood'?

I received an email recently asking about the so-called 'Great Spokane Flood' that occurred some 13,000 years ago at the very end of the last major ice age.

In geological terms, this was one of the biggest floods on earth. It has been known by several names, including the 'Glacial Lake Missoula Flood' and the 'Bretz Flood.' This massive flooding entirely changed the topography of the Inland Northwest.

Tongues of ice nearly a thousand feet thick from a huge continental glacier dammed up an enormous lake in western Montana called Glacial Lake Missoula. When the water level rose enough to 'float the ice dam' like a giant ice cube, the ice dam suddenly broke, sending a towering wall of water through what is now northern Idaho, eastern Washington State and the Columbia River Basin.

For many weeks before the waters subsided, much of the Inland Northwest from Spokane and Coeur d'Alene to Portland, Ore., lay submerged beneath an ocean of water some 500 feet deep.

Murky, silty floodwaters left behind the 'Scabland Coulees' that we see today in eastern Washington.

The massive Inland Northwest flooding of 13,000 years ago happened not just once, but repeatedly, as Glacial Lake Missoula's water level rose high enough to 'float the ice dam' over and over again, causing more devastation down-stream with each flood.

A visit to the Missoula Valley in western Montana will detail literally dozens of past shorelines on the eastern hillsides of Mount Jumbo.

Spokane and Coeur d'Alene were hit dozens of time by Glacial Lake Missoula's floods. As these vast waters deepened and widened, they created the only significant gap in the entire length of the Cascade Mountain Range, the spectacular Columbia River Gorge.

If one wants more details on Glacial Lake Missoula's floods of 13,000 years ago, pick up a copy of David Alt's book, "GLACIAL LAKE MISSOULA AND ITS HUMONGOUS FLOODS," published by Mountain Press in Missoula, Mont. The phone number is 1-800-234-5308, or go online at www.mtnpress.com.

NORTH IDAHO WEATHER REVIEW AND LONG-RANGE OUTLOOKS

Following unusually cold and snowy weather conditions in both December and January across North Idaho, the first 16 days of February turned mild and snowless throughout the Inland Empire.

Flowers bloomed prematurely in area gardens. Afternoon highs reached the low to mid 50s by Feb. 15. According to some, the spring of 2013 had arrived six weeks ahead of schedule. Many removed their winter tires from their vehicles despite our warnings that Old Man Winter wasn't done with us just yet.

As Randy Mann and I predicted, frequent snow showers returned to the region during the last 12 days of February. Nearly 9 inches of the white stuff fell at my weather station on Player Drive during the period. The maximum reading on Thursday, Feb. 21, was just 35 degrees. The morning low was a frigid 24 degrees, February's chilliest reading. Area roadways became extremely icy. There were scores of 'fender-benders.'

Our total liquid precipitation for February, including melted snow, was a below normal 1.71 inches. Our usual February precipitation since at least 1895 has been 2.17 inches.

Our total February snowfall was 8.7 inches. That compares to the 118-year normal of 11.9 inches in Coeur d'Alene. As of March 1, our 2012-13 seasonal snowfall total stood at 70.4 inches, just above the normal snowfall of 69.8 inches for an entire season ending June 30.

Looking farther down the meteorological highway, we see a slightly cooler and wetter than normal spring season again this year due to a chilly La Nada/La Nina sea-surface temperature event in the waters of the eastern Pacific Ocean.

But, the 'good news' is that it won't be as damp as the wettest spring on record in 2012, when we saw record wet months in March, 7.51 inches and 5.84 inches in June. Snowfall for the rest of this season should be under 10 inches in town into early April. Those studded tires can soon come off.

The summer of 2013 weatherwise still looks GREAT!

SPORTS NOTE

March weather has been mild and dry, but it's off to a striking start, as far as our own Randy Mann is concerned! Randy rolled a rare perfect game - a 300, with all 12 balls being strikes - during league competition Friday at Sunset Bowl.

Cliff Harris is a climatologist who writes a weekly column for The Press. His opinions are his own. Email sfharris@roadrunner.com