Goat Island Mountain

From about 6000' on the southeast slope of Goat Island Mountain (foreground), Mt. Rainier (14410') is spectacular with the massive Emmons Glacier flowing down from the summit to the right. Goat Island Mountain (7288') is 6 miles northeast of Mt. Rainier and 2 miles south of Sunrise.

Little Tahoma Peak (11138'), the third highest mountain in Washington, is the rocky peak to the left. The Frying Pan Glacier, on its NE flank, extends from 9900' to 7000' and terminates in ice cliffs up to 200' high.

Like most volcanic rock, Little Tahoma Peak is subject to rockfall.

A dramatic example occurred during December of 1963. A series of seven rockfalls, with a total volume of approximately 14 million cubic yards, cascaded off the north face of Little Tahoma Peak onto the Emmons Glacier, several thousand feet below. The falls were not observed, but their short-lived histories are reconstructed by a careful study of the blanket of rock debris that covered the glacier and the head of the White River valley beyond. The falling rock and snow were propelled downvalley as a rock avalanche by the slope of the Emmons Glacier. It formed a very buoyant cloud of debris that traveled more than 4 miles and contained rocks weighing hundreds and even several thousand tons. An estimated of the velocity was made by noting the height the debris reached as the rock avalanche banked off obstructing walls. The speed attained was greater than 60 miles per hour - perhaps as much as 100 miles per hour. These were not mudflows - in fact, water had little to do with them. Instead, they were turbid clouds of rock debris, flowing downhill on a cushion of air trapped and compressed beneath the rapidly moving front.

Cascadia: The Geologic Evolution of the Pacific Northwest, Bates McKee, McGraw-Hill, 1972, pp206-207.

The north face is the right skyline of the peak in the image. The average power released in each rockfall was on the order of 100,000 megawatts, if I did the numbers properly.

From just west of the summit of Goat Island Mtn., the view southeast includes Tamanos Mtn. (6790', left), pyramidal North Chimney (7035'), Cowlitz Chimney (7605') and Banshee Peak (7431'), just right of center). This image is linked to a pair of stereo images.

Averaged over 1 hour, our peak ascent (descent) rates were 1120 ft/hr (-1950 ft/hr) at 11:30AM (5 PM). These data were logged by an altimeter watch.

You are visitor number access counter

Return to my home page