Washington
If the box-shaped peninsula you see from high over northwest Washington State looks tacked on to the edge of the continent, it’s because it was. Plate tectonics created the western edge of North America over millions of years, periodically adding chunks of land that were once separate from the main landmass. One of the best examples of this accretionary process is the Olympic Peninsula, which was connected to the Pacific Northwest coast around 35 million years ago.
The creation of the peninsula started with the eastward movement of the oceanic Farallon Plate, which was eventually subducted under the continental North American Plate. As the Farallon Plate was shoved underneath the overriding plate, some of the Farallon Plate was scraped off by the edge of the North American Plate, where it piled up and jammed against the edge of the continent. This created a dome of seafloor material that would later be uplifted and carved by glaciers into the snowcapped Olympic Mountains you can see from the air, in the middle of the peninsula.
Thus, these mountains—the highest is Mount Olympus, at 7962 feet—are actually composed of rocks that once sat on the floor of the Pacific Ocean. The material is volcanic basalt that weathers into crumbly, dark rock. And it weathers a lot: the western slopes of the peninsula are the wettest place in the United States, receiving in excess of seventy feet of snow and twelve feet of rain each year.
All that moisture feeds more than 180 existing glaciers within the boundaries of Olympic National Park, which covers a majority of the peninsula’s interior. The largest ice mass is Blue Glacier on Mount Olympus, which covers just under two square miles of rough alpine terrain, over 900 feet thick. The Olympics receive a lot of moisture, but the Olympic glaciers are still shrinking at an alarming rate, because of higher year-round temperatures. The Blue Glacier has shrunk nearly a mile in length since the 1800s and the ice is 200 feet thinner. In 2009, an updated glacier inventory found that Olympic National Park had 184 glaciers, down from 266 in 1982. If you had flown over the peninsula in the late 1970s and again in 2009, you would have seen a 34 percent loss of ice in just thirty years.
At lower elevations, wet conditions have also spawned a moss-covered temperate rainforest—one of the rarest biomes on Earth. Temperate rainforests once thrived from southern Oregon to southeast Alaska, but they now exist in North America only in a few protected pockets like this one. A unique adventure in the Olympics involves hiking from the Pacific Ocean through a rainforest to a glacier: The Hoh River Trail runs for eighteen miles along the glacier-fed Hoh River up to its headwaters at the Blue Glacier, in the shadow of Mount Olympus.
Oceanic basalt weathers into very crumbly rock, as seen here on the side of Mount Angeles in the Olympic Mountains.
Clear-cuts mar the view across Olympic National Park, toward Mount Olympus, the highest summit in the background.
Look for the snowcapped Olympic Mountains flanked by lush green rainforest, on a boxy piece of land surrounded by ocean and inner waterways, in the northwest corner of Washington. You may fly over the Olympic Peninsula en route to Seattle, Washington; Portland, Oregon; or Vancouver, BC.
