Mount Deception (Washington)

Mountain in Washington (state), United States

Mount Deception is a peak in the Olympic Mountains of Cascadia. It is in Olympic National Park on the Olympic Peninsula in the U. S. state of Washington.

At 7788 feet (2374 m) high Mount Deception is the second highest peak of the Olympic Mountains, after Mount Olympus. It is the highest peak of the eastern Olympics. Mount Deception's prominence is 4108 feet (1252 m), making it the 17th most prominent peak in Washington. Its nearest higher peak is Mount Olympus at 21.79 mile (35 km) to the west. This location puts it in the rain shadow of the Olympics, resulting in far less precipitation than Mount Olympus and the western Olympics receive. Mount Deception sits on the boundary between the drainage basins of the Dungeness River, to the north, and the Dosewallips River, to the south and east. Deception Creek, a tributary of the Dosewallips River, drains the southern slope of Mount Deception. Gray Wolf Pass is located about 1 mile (2 km) west of Mount Deception. The pass connects the Dungeness and Dosewallips drainage basins. The adjacent Needles are typically regarded as providing better, and somewhat more difficult, mountaineering objectives in the Royal Basin area.

Based on the Köppen climate classification, Mount Deception is located in the marine west coast climate zone of western North America. Most weather fronts originate in the Pacific Ocean, and travel northeast toward the Olympic Mountains. As fronts approach, they are forced upward by the peaks of the Olympic Range, causing them to drop their moisture in the form of rain or snowfall (Orographic lift). As a result, the Olympics experience high precipitation, especially during the winter months. During winter months, weather is usually cloudy, but, due to high pressure systems over the Pacific Ocean that intensify during summer months, there is often little or no cloud cover during the summer. In terms of favorable weather, the best months for climbing are June through September.

The Olympic Mountains are composed of obducted clastic wedge material and oceanic crust, primarily Eocene sandstone, turbidite, and basaltic oceanic crust. The mountains were sculpted during the Pleistocene era by erosion caused by glaciers advancing and retreating multiple times.