Cascadia Earthquake of 1700



On the evening of January 26, 1700 at around 9 PM, an unexpected event shook the natives and their Gods along the Pacific Northwest. This recorded 9.0 magnitude earthquake caused repercussions felt as far as Japan with huge tsunamis thrashing the coastline. This is one of the biggest earthquakes to ever be conceived to have happened based off of geological and folklore evidence.
The Cascadia earthquake occurred at the convergent plate boundary of the Juan de Fuca plate and the North American plate, (see Figure 1). This area along the Pacific Northwest Coast where the oceanic Juan de Fuca plate meets the continental North American Plate is knows as the Cascadia subduction zone. The Subduction zone is approximately 1000 km in length and reaches from Vancouver Island to Northern California just 80 km offshore. The Cascadia Earthquake has recently been compared with the recent ~9.0 magnitude earthquake in Sumatra, (see Figure 2).

It is hard to know if this event occurred because of how long ago this event was thought to have happened. What we do know is that there are many pieces of evidence that complete the puzzle to the possibility of the Cascadia Earthquake. To confirm that this event took place, experts look at geological evidence as well as Native folklore to establish and see if this incident did in fact occur.

When looking at geological evidence, you can see that there are many conclusive facts that prove the existence of this event. With the use of modern technology it is easier to see what lies in the soil and what type of material is present in each layer. When samples were taken, sand was found below many layers of soil which lends its self to believe that a tsunami caused by the earthquake brought the sand inland, (Figure 3).

There is also evidence with the areas along the coast with the help of the trees that died in the wake of the earthquake and tsunami. Earthquakes are known to cause subsidence, a down drop of land to a lower level, and the Cascadia earthquake did just that, (Figure 4). The subsidence from the earthquake caused the land level to go below sea level and thus killing the trees located in the area of subsidence. Salt water filled up the land and the trees could no longer survive. This area is often referred to as the ghost forest, (Figure 5).

Tree rings is also another source of information about the time frame in which this earthquake took place. With the use of carbon-14 dating, samples of living trees in the same area were taken and then compared to the trees in the Cascadia ghost forest. When looking at the samples from both trees, the growth patterns matched exactly until when the proposed earthquake occurred. With the use of tree ring analysis, it confirms that the time of the earthquake coincides with the estimated time that the trees died, after the 1699 growing season and before the 1700 growing season.

To further confirm the presence of this earthquake, there are tsunami records in Japan. Some skeptics say that the tsunamis that hit the coast of Japan could have been caused by other earthquakes in another area. There have not been any other records of earthquakes recorded around that time the tsunamis allegedly struck the coast of Japan. To cause the same type of tsunamis in Japan, it is safe to say that the Cascadia earthquake was the immediate cause of the tsunamis. With current tsunami calculations, including the approximate size and speed that the waves would have been traveling, it confirms the time and date of the previous thought tsunami, 9 PM on January 26, 1700.

One other piece of evidence is the Indian folklore of the native that resided along the Pacific Northwest. There were numerous tribes that had settled in the region. Makah, Quileute, Hoh, Klallam, Haida, Clatsop, Yurok and Modoc were just a few of the many Indian nations that settled there. Although about 95% of native oral traditions have been lost because of the European settlement in the area, there are still numerous records that describe events such as violent shaking, flooding, and whole villages being washed away. There are a broad number of stories which have been documented among which some are able to be dated and others can not. Taking into account all of the stories that are able to be dated, the average midpoint date is 1701, which is very close to the proposed date of 1700. It is also believed that their gods were in battle and that is what caused the horrible event. These two gods were Thunderbird and Whale and have been frequently sited in many stories and tales of shaking and tsunami like activity from Vancouver to northern Oregon. Whale is thought of as a mammoth whale in which all of creation rests and Thunderbird causes thunder with just a move of its feather and brings rain from the lake that sits upon its back, (Figure 6). Ideas of the Cascadia earthquake show Thunderbird and Whale creating this event as follows. “Shaking and ocean surges can be inferred from the story of Thunderbird driving his talons deeply into Whale’s back, and Whale diving and dragging the struggling Thunderbird to the bottom of the ocean…” (Source 1) The story that follows is a Hoh and Quileute myth and tells the tale of the battle between the Thunderbird and the Whale. It seems to speak specifically to a Tsunami type event such as the water first withdrawing out to sea and then “submerging the whole country”.


From “Some Additional Myths of the Hoh and Quileute Indians” by Albert B. Reagan, 1934:
A STORY OF THE FLOOD
“In the beginning Kwattee created the animals of the earth. Then by the union of some of these animals with a star which fell from heaven, came the first human beings. And from these sprang the various races of men.
Years came and went and all was good. Then Chief Thunderbird attempted to destroy all the good whales of the ocean. Kwattee then interfered, and a terrible drawn battle was fought between him and Thunderbird.
Enraged, that bird caused the waters of the great deep to rise. For four days the sea continued to rise. It rose till it covered the very tops of the mountains.
Again Kwattee joined his adversary in battle, and while the conflict was in progress, the waters receded. This engagement, too, was a drawn battle, and following it the waters again rose. The water of the Pacific flowed through what is now the swamp and prairie westward from Neah Bay on the Strait of Juan de Fuca to the Pacific, making an island of Cape Flattery.
Again Kwattee and Thunderbird engaged in terrible conflict, and again the waters suddenly receded, leaving Neah Bay, the Strait of Fuca, and Puget Sound perfectly dry. For four days the water ebbed out, and numerous sea monsters and whales were left on dry land.
The battle was again indecisive. Then without any waves or breakers the waters again rose till they had submerged the whole country. Then Kwattee killed Chief Thunderbird. The waters were then four days receding. And since then there has been no great floods on the earth. Also each time that the waters rose, the people took to their canoes and floated off as the winds and currents wafted them, as there was neither sun nor land to guide them. Many canoes also came down in trees and were destroyed, and numerous lives were lost. And the survivors were scattered over the whole earth. One segregation of the Quileutes found themselves at Hoh, another at Chemakum (near the present Port Townsend), and a third succeeded in returning to their own home here on the Pacific.”


Other Indian lore seems to combine mythological story telling with more historic possibilities, such as the following Klallam tale.


From “Klallam Folk Tales” by Erna Gunther, 1925:
THE FLOOD
“There was a man who told his people to make some canoes and to make them large and strong so they could endure storms. There was a flood coming. The people said the mountains were high and they could just go up the mountains when the flood came. He warned them again. Soon it began to rain and rained for many days. And the rivers became salt. The people said they would go up the mountains. When the flood came they took their children by the hand and packed the small ones on their backs. It became so cold that the children died. They had no way of getting to the mountains for the valleys were full of water and the rivers overflowed their banks.
The people that walked all died. Those that had canoes and water and food lived. Some who were in a canoe tied themselves to a treetop when their canoe hit the tree and split. Many died. Some tied themselves to mountains and the highest ones were saved. The flood uprooted all the trees. That is why there are no really large ones left today. All the trees of today grew after the flood.”


Several other stories can be found spread throughout the geographic region. Sprinkled among them are thematic links that suggest the kind of activity that might be found in a subduction zone or that hint at a tsunami type of event. Details of such activities in these stories are difficult to pinpoint precisely.

Besides the native folklore, other evidence such as soil records, subsidence, tree ring records and Japan tsunami records all help to show that this earthquake did occur and also to better understand this event. For we know that this event did happen and therefore could and most likely will happen again.


Figure 1


CascadiaSubduction-Sci-52501c.gif
The Juan de Fuca plate, North American plate,
And the Cascadia Subduction Zone.

Figure 2


Cascadia_subduction_zone_USGS.png
The Cascadia Subduction Zone
V.
The Sumatra Rupture Zone

Figure 3


SoilHorizons.jpg
Layer of sand in the soil layers.

Figure 4


UpliftandSubsidence.jpg
How subsidence occurs during an earthquake.

Figure 5


GhostForest.jpg
The creation of the 'Ghost Forest'.

Figure 6


thunderbird.JPG
Thunderbird and Whale.




Sources
http://www.pnsn.org/HIST_CAT/SRL76-2Ludwin.pdf

http://ajdubre.tripod.com/Physics/CascadiaSubduction-Sci-52501.html

http://earthquake.usgs.gov/regional/pacnw/paleo/greateq/

http://earthquakescanada.nrcan.gc.ca/historic_eq/15-19th/1700/1700_e.php

http://www.pnsn.org/HIST_CAT/STORIES/draft1.html

http://www.pnsn.org/HIST_CAT/STORIES/legend.html

http://www.pnsn.org/HAZARDS/CASCADIA/cascadia_event.html