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Olympic National Park Geology
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The Olympic Mountains are not very high. Mount Olympus, the highest, is just less than 8,000 feet. Although they are not high 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 some 200 inches falling mostly as snow.
A number of new theories have been presented recently regarding the origin of the Olympics. Geologists continue to discover new information that contributes to the debate. The following theory is the one that has been accepted for a number of decades.
These mountains have arisen from the sea. For eons, wind and rain have 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 landmass. 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.
Surrounded on three sides by water and still crowned by alpine glaciers, the Olympics retain the distinctive character that developed from their isolation. Several plants and animals are unique to the Olympics. They are examples of how genetic diversification occurs when geographical isolation exists. The most striking example is the Olympic marmot, with its distinct chromosonal and behavioral patterns. Others included Flett's violet, Piper's bellflower, Olympic Mountain synthyris, Olympic chipmunk, Olympic snow mole, and Beardslee and Cresceti trout, as well as others.
Glacial ice is one of the foremost scenic and scientific values of Olympic National Park. 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. In the company of these glaciers are perpetual snow banks that have the superficial appearance of glacial ice. Because they are lacking in the criteria below, they are not true glaciers.
True glaciers are structurally three layered bodies of frozen water. The top layer is snow; the middle neve, or mixed snow and ice; and the bottom layer is of pure ice, which is quite plastic in nature. Crevasses or deep cracks in the glaciers form as the ice is subjected to uneven flow over alpine terrain. Another structural feature is the bergschrund, which is a prominent crevasse-like opening at the head of the glacier where the ice has been pulled away from the mountain wall.
The rate of glacial flow is quite variable and Olympic glaciers are "slow-moving" in contrast to some in Alaska, which occasionally move at the rate of several hundred feet per day for short periods of time. There is no great advance of Olympic glaciers today, but there is not a rapid melting back of the ice either. Forward surges in glacial flow often occur after a number of very heavy winters and cool summers, but such activity has been relatively infrequent with Olympic glaciers in recorded time.
Snow nurtures the glaciers in the accumulation zone or at the origin of the ice. Most of the melting or ablation occurs near the termini or snouts of the glaciers. A vigorous glacier will be maintained by a heavy accumulation of snow in the winter and only average melting during the summer. The freezing point in late spring and precipitation in early fall appear to be critical items in relation to this gain and loss. Excessive melt before and after the normal melt season would result in an impoverished budget for the following year.
The movement of glacial ice, past and present has produced striking geological features in the Olympic Mountains. The lake basins, U-shaped valleys, and jagged peaks are the products of massive glacial erosion that occurred many thousand of years ago when the year around climate was much colder. This erosion process continues today, but on a much smaller scale. As glaciers advance and retreat, rock is plucked, transported, and deposited by moving ice. The deposition of rock results in medial (middle), lateral (side), and terminal (end) moraines. In many cases, a terminal moraine to create a lake basin will dam a glacially created bowl (cirque) at the head of a valley. The finely ground rock created by the glaciers often makes the glaciated rivers look milky when the glaciers are melting.
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Olympic National Park Climate
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Olympic National Park climate is predominantly a marine type with cool summers, mild but rather cloudy winters, moist air, and a small daily range in temperatures. The weather is extremely unpredictable. Rainfall is quite varied. Sequim, on the northeast side of the peninsula receives an average of about seventeen inches of precipitation a year. While forty airline miles to the west, in the rain forest valleys, precipitation can average 140 to 167 inches per year. Seventy-six percent of the yearly precipitation falls during the six months between October first and March thirty -first. There is no definite time for the beginning and ending of the dry or rainy seasons. The transition is gradual and variable.
The winter season can have afternoon temperatures in the 40�s and night time readings are usually in the upper 20�s or lower 30�s. In lower elevations and near the water, snow rarely exceeds a depth of six to ten inches or remains on the ground more than a few days. However, snowfall and depth on the ground increases dramatically along the slopes and tops of the mountains.
Spring is mostly wet, mild and often windy. Higher elevations are cooler with possible snow flurries. Temperatures usually range from 35� F to 60� F.
Summer is generally fair and warm. Afternoon temperatures in the warmest summer months average from 65� F to 70� F, occasionally reaching 80� F A temperature of 85� F is considered unusually warm. Night time temperatures can drop as low as 45� F. Frequently, during the latter half of the summer and early fall, fog banks and low clouds form over the ocean and move inland at night. Tops of the clouds are generally below 3000 feet; thus higher elevations are sometimes clear while the lower valleys are filled with fog. Fog sometimes disappears before mid-day. On most summer afternoons near the water, a moderate to cool breeze can be expected. A few thunderstorms usually occur each summer, especially in the higher elevations. Normally very little rain falls during the summer months but it has also been known to rain for several days during this period.
Fall is usually cool and wet with occasional winds. Early snow storms are possible in the mountains. Temperatures usually range from 35� F to 65� F.
Elwha Ranger Station Olympic National Park Weather Stats
Month Avg High - �F Avg Low - �F Avg Precip (in) Avg Snowfall (in) Avg Snow Depth (in)
Jan 40.8 30.8 8.94 8.2 1.0
Feb 45.3 32.6 7.28 2.4 1.0
Mar 50.1 33.9 5.91 1.5 1.0
Apr 56.8 37.2 3.35 0.0 0.0
May 63.9 42.0 1.75 0.0 0.0
Jun 68.2 46.5 1.17 0.0 0.0
Jul 73.9 49.9 0.76 0.0 0.0
Aug 74.1 50.8 1.16 0.0 0.0
Sep 68.5 47.4 1.90 0.0 0.0
Oct 57.2 41.0 5.21 0.0 0.0
Nov 46.6 35.6 9.23 1.3 0.0
Dec 42.0 32.4 9.84 3.6 0.0
Annual 57.3 40.0 56.50 17.1 0.0
PRECIPITATION AVERAGES
Port Angeles�Spring: 1.32 inches per month average, Summer: .67 inches per month average, Fall: 2.45 inches per month average, Winter: 3.76 inches per month average. Average inches per year--24.6
Staircase (Lake Cushman) --Spring: 6.60 inches per month average, Summer: 1.70 inches per month average, Fall: 9.40 inches per month average, Winter: 15.71 inches per month average. Average inches per year--100.25
Kalaloch (Ocean Beaches) --Spring: 8.94 inches per month average, Summer: 3.13 inches per month average, Fall: 11.17 inches per month average, Winter: 17.12 inches per month average. Average inches per year--103.0
Hoh (Rain Forest) --Spring: 10.33 inches per month average, Summer: 3.33 inches per month average, Fall:13.00 inches per month average, Winter: 18.33 inches per month average. Average inches per year--135.0
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