Greetings from the Olympic Peninsula!
We hope everyone is continuing to be healthy and safe! This week's newsletter is a concise look at the geological and human history of the Olympic Peninsula. Enjoy!
has six volcanoes along its segment of the Pacific Ring of Fire; Mount Saint Helen’s is currently the most active having awoke recently for a short time in 2008. The massive ridge of volcanoes, which extends from Northern California to southern British Columbia, is called the Cascade Range and is 700 miles long, with an average width of about 80 miles and has a total of thirteen volcanoes.
The Olympic Peninsula
is located 90 west of the Cascade Range and if you viewed the Olympic Peninsula from above, nearly right in the center you would see the glacier capped summit of Mount Olympus rising to an elevation of 7,980 feet and you would easily assume that Mount Olympus is also a volcano and that which created the Olympic Peninsula, but you would be very wrong. If you hiked to the summit, you could easily visualize the summit edges forming a crater like shape, but you would be very surprised to find the mountain is almost entirely made of sedimentary rock. Sedimentary rock at nearly 8,000 feet? What is going on? Well, travel back in time with me to see what geology can tell us.
is generally created over eons of time when rock is eroded into small particles, mainly via wind and water, and then flows to the bottom of the ocean where it is compressed and hardened into a new layer of rock. On the Olympic Peninsula this compressed sediment mostly creates shale.
Over time there are different geological events that can create a specific type of erosion period, which can be represented by individual layers of sedimentary rock.
For millions of years on the western edge of the North American continental landmass, which later would become the Olympic Peninsula, much of the ocean floor was layered by massive flows of sediments in the form of turbidites. Turbidites are sediments that are moved by high-density water flows similar to a slurry and those flows can carry larger rocks further and deeper into the ocean depths. Sometimes turbidites are the result of underwater landslides and all these different forms of movement create a specific type of settling and sifting of debris, which is the story of the Olympic Peninsula that the rocks can tell us.
Magma, Lava and Volcanoes
About 34 million years ago, while all the sediments and turbidites where tumbling to the ocean floor, the Pacific and North American tectonic plates where on the move and the unlucky Farallon Plate was caught in between. The Pacific Plate is oceanic, which makes it more dense and heavier than the North American Plate and so the Pacific Plate slides under the North American Plate in a process that is called subduction. But what about the Farallon Plate? It has mostly been crushed and compressed underneath the leading edge of the North American Plate and today it exists as three very small remnant tectonic plates: The Explorer, Juan de Fuca, and Gorda Plates. But the Farallon Plate was fairly large, so what happened to the huge mass of land? Well, most of it was compressed deep into the Earth's crust and was heated and reformed into magma. The huge volume of magma (molten rock beneath the earth’s surface), which created immense pressure that built up under the western leading edge of the North American Plate, was released vertically and vented through volcanoes in the form of lava (magma that reaches the earth’s surface). Voilà!
Accretion Debris and Slabs
: Although most of the Farallon Tectonic Plate was crushed beneath the western edge of the North American Plate, that leading edge of the North American plate has significant weight that cut into and scraped off the top layers of the Farallon Plate and the extremely large pile of debris that landed on top of the western edge of the North American Plate is called “Accretion”. This process of accretion and uplift is responsible for creating mountains as far east as the Rocky Mountains: You got to really think BIG, when it comes to geology. And so, what is the Olympic Peninsula? It is nothing more than a huge pile of accretion debris.
Besides sedimentary rock, however, there are other types of rock on the Olympic Peninsula, mainly basalt, which is an extrusive igneous rock. This rock type has volcanic origins, but was created from eruptions on the ocean floor where the lava cooled quickly while it was exposed and then later through tectonic uplift and erosion has made it to the surface. Often these types of basalt formations are called “Pillow Lava”. In Olympic National Park, the Klahhane Ridge area, including Mount Angeles, has risen up to an elevation of 6,453 feet, having once been on the ocean floor and it is a great example of pillow lava.
There probably is some granite that originates from beneath the Olympic Peninsula, but granite is an intrusive igneous rock; meaning it formed and cool slowly beneath the earth’s surface and then later through tectonic uplift and erosion has made it to the surface and it is unlikely this event happened in a subduction zone in the Pacific Northwest. Most of the granite on the Olympic Peninsula probably originated in Canada and was brought to the peninsula by riding and being pushed along by numerous glaciers over time; perhaps even traveling a 100-miles or so from the source of origin in the Canadian Cascades. On the north side of the Olympic Peninsula when we hike along the beach, we find a lot of smooth granite rocks which have been polished by both the glaciers and the ocean, but if you travel down the west coast; you will find less and less granite the further south you go.
Sunshine at last!
The rocks atop Mount Olympus are about 50 million years old, but have seen sunlight for only about 12 million years. If you get a chance to visit Hurricane Ridge in Olympic National Park at an elevation at 5,242 feet, you will find a lot of sedimentary rock and interestingly, most of it is laying on its side from having been pushed and folded onto itself during the accretion process. It is estimated that there could be as much as 12 miles of “Siletzia” accretion atop the subducting slab below, most of which is still below sea level. The Olympic Peninsula and Mount Olympus are just the tip of the accretion wedge. Don’t forget to think really BIG!
And then came the glaciers:
Periods of glaciation have come and gone for about 2.6 million years. These numerous glaciers have been the sculptors of the land, another form of erosion, but one that leaves incredible beauty behind when it recedes. The Cordilleran Ice Sheet and the Vashon Glacial Period are partly responsible for the shape and face of the Pacific Northwest.
And then came the people:
About 16,000 years ago the last glaciers started to recede and life quickly arrived and flourished on the newly exposed lands. The Olympic Peninsula has nine native tribes, which are descendants from the first people and it is believed humans have been on the peninsula for about 12,000 years.
And then came more people:
Explorers from Europe started arriving along the coast as early as 1513 and the Spanish Conquistador Vasco Balboa, claimed the Pacific Northwest for Spain. Then came the English, then the French and then the Americans, it’s long story…. By 1818, the Pacific Northwest was part of what the United States called Oregon Country. In 1862, President Lincoln designate 3,500 acres of land on the Olympic Peninsula as a federal reserve for military purposes, (this land would later become the town of Port Angeles). On November 11, 1889, Washington became the 42
The Evergreen State
Preservation of the Olympic Peninsula
goes back to President Grover Cleveland, who established the Olympic Forest Reserve in 1887. By the late 1800's, logging the old growth forest was well underway and early explorers and conservationists urged the federal government to slow the logging and protect the forests. With the establishment of the National Forest Service in 1905 by President Theodore Roosevelt, the Olympic Forest Reserve, previously controlled by the Department of Interior, was transferred to the National Forest Service within the Department of Agriculture. During this time, the movement to establish national parks and preserve the west was in full swing. In 1909, by an act of executive order, Teddy Roosevelt established the Olympic National Monument to protect the habitat of the huge herds of elk that reside on the Olympic Peninsula. Teddy Roosevelt was a big game hunter and understood that all animals need intact and healthy habitats for survival. For twenty-nine years after that, it was a big political battle to move the designation of Olympic National Monument to Olympic National Park. Olympic National Park was established in 1938 and the paperwork was signed by President Franklin Roosevelt (Teddy’s distant cousin). Olympic National Park currently protects 922,650 acres. The trees of the Olympic Peninsula where so valuable as a timber source, for many it was seen as an economic mistake not to sell the trees to support the economy and create jobs. During WWII and long afterwards, large amounts of Sitka Spruce trees were harvested, both legally and illegally for use in the building of airplanes. Sitka Spruce trees have the best weight to strength ratio and made excellent material for aircraft. It is not a coincidence that Boeing started building planes in Washington state.
For extra credit! National Park vs National Monument
: A president can create a national monument, but only congress can create a national park. Here is why it matters: The Antiquities Act of 1906 authorizes a president to proclaim national monuments on federal lands that contain historic landmarks, structures, or objects of historic or scientific interest. This law was created to enable a president to act quickly when needed and is not a permanent act and any president that follows can reverse that decision, which happens every time we have a new president, especially in regards to land. In contrast, to create a national park, it is decided by congress and this takes time, debate and compromise. It is a long process, which involves the voices and wishes of the American people and the final creation of a national park is viewed as permanent after the president signs the paperwork. The congress can also create national monuments. For example: Both President Clinton and President Obama set aside large tracts of land as national monuments, only to have those decisions reversed by the succeeding presidents, but a president cannot undo a national park.