DESCRIPTION:
Olympic Mountains

Consider the Olympic Mountains to be an ancient sea floor that has been wedged into the North American Continent and uplifted into the atmosphere by surrounding geologic pressures. As the topmost layer of the sea floor is scraped off and crumpled on to the North American Plate, the lower branch dives beneath Olympic creating heat and pressure that eventually form the volcanoes of the Cascades.

To the north and east of the Olympic Peninsula lie the Strait of Juan de Fuca and Hood Canal. These bodies of water along with Puget Sound were carved by ice sheets over 13,000 years ago.

The Olympic Mountains are not very high -- Mount Olympus, the highest, is just under 8,000 feet -- but they rise almost from the water's edge and intercept moisture-rich air masses that move in from the Pacific. As this air is forced over the mountains, it cools and releases moisture in the form of rain or snow. At lower elevations rain nurtures the forests while at higher elevations snow adds to glacial masses that relentlessly carve the landscape. The mountains wring precipitation out of the air so effectively that areas on the northeast corner of the peninsula experience a rain shadow and get very little rain. The town of Sequim gets only 17 inches a year, while less than 30 miles away Mount Olympus receives over 220 inches falling mostly as snow.

There are about 266 glaciers crowning the Olympics peaks; most of them are quite small in contrast to the great rivers of ice in Alaska. The prominent glaciers are those on Mount Olympus covering approximately ten square miles. Beyond the Olympic complex are the glaciers of Mount Carrie, the Bailey Range, Mount Christie, and Mount Anderson.

For a period of thirty-seven years, from 1774 to 1811, Nootka Sound was the best-known and most-frequented harbor on the Northwest Coast of America. The first date is given is that of the harbor's discovery by the Spaniard, Juan Perez, and the second that of the founding of Astoria at the mouth of the Columbia River. ... "On proceeding south, on August 10, 1774, Perez saw in latitude 48 degrees 10 minutes, a beautiful snow-white mountain, which he named Santa Rosalia. Fourteen years later it was rechristened by John Mears, the English captain, and from that time it has been known as Mount Olympus."

These mountains have arisen from the sea. For eons, wind and rain washed sediments from the land into the ocean. Over time these sediments were compressed into shale and sandstone. Meanwhile, vents and fissures opened under the water and lava flowed forth, creating huge underwater mountains and ranges called seamounts. The plate(s) that formed the ocean floor inched toward North America about 35 million years ago and most of the sea floor went beneath the continental land mass. Some of the sea floor, however, was scraped off and jammed against the mainland, creating the dome that was the forerunner of today's Olympics. Powerful forces fractured, folded, and over-turned rock formations, which helps explain the jumbled appearance of the Olympics. Radiating out from the center of the dome, streams, and later a series of glaciers, carved peaks and valleys, creating the beautiful, craggy landscape we know today. Ice Age glacial sheets from the north carved out the Strait of Juan Fuca and Puget Sound, isolating the Olympics from nearby landmasses.

In the past, a vast continental ice sheet, descended from Alaska, south through British Columbia to the Olympics. The ice split into the Juan de Fuca and Puget ice lobes, as they encountered the resistant Olympic Mountains. A glacial outwash stream surged around the southern end of the peninsula to the Pacific Ocean. This isolated the Olympic Peninsula from the nearby Cascade Mountains and limited species from entering and exiting the peninsula. When the ice sheet reached the Peninsula, large areas of the continental shelf were also exposed by the lower sea levels since so much water was trapped as ice. This created a coastal refuge. The distance from Mount Olympus to the Pacific Ocean may have been double that of today.

The Fraser glaciation lasted about 10,000 years and consisted of 3 stades (periods of ice expansion) and 2 interstades (ice recession). The Fraser ice advance in the Olympics began with expansion of alpine glaciers -- the Evans Creek stade. Although poorly dated on the Olympic Peninsula, at maximum advance -- about 21,000-19,000 B.P.(before present) -- glaciers extended down west-side valleys. Glaciers in east-side drainages were smaller and were restricted to upper valley areas or headwalls. The Evans Creek advance coincided with the beginnings of an enormous ice buildup in the mountains of British Columbia.

Alpine glaciers retreated to undetermined positions up valleys following the Evans Creek stade. This brief interstade was followed by advance of Cordilleran ice sheet from British Columbia into the Puget Sound area -- the Vashon stade. The ice reached its maximum extent around 15,000 B.P., splitting into the Juan de Fuca and Puget ice lobes as it encountered the Olympic Mountains. Ice at the northeast corner of the Olympics was at least 3,800 feet thick at maximum advance. The Vashon ice produced glacial lakes behind massive ice dams that formed in the northern and northeastern river valleys. The ice sheet apparently did not contact the remaining alpine glaciers. The spatial and temporal relations between ice sheets and alpine glaciers have important implications for the biogeography of endemic taxa; suitable habitat for alpine plants evidently persisted in or near the Olympic Mountains during both alpine and ice sheet advances of the Fraser glaciation.

The Vashon advance was short-lived; by 13,600 B.P., the two lobes had receded into a single lobe located in the northern Puget lowlands. A minor readvance (the Sumas stade) occurred about 11,500 B.P., but the extent and climate significance of this stade has been questioned. The Fraser glaciation ended about 10,000 B.P. when major climatic changes occurred.

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