It is time to consider the largest documented earthquake in Washington state, or at least the largest earthquake which occurred after white man came to the region in the latter 1700s. This massive earthquake occurred in 1872. It is important to examine certain facets of this quake, because it helps to better understand the geology of the Cascadia region.
A Seattle Time page, linked here states that on the west side of the Cascades, "fissures split the ground south of Seattle [which] led early observers to assume the quake was centered under Puget Sound. But, scientists are currently looking at the Spencer Canyon fault, on the east side of the Cascades near Entiat, Washington, as being the culprit for the 1872 quake. The Spencer Canyon fault is one location where an earthquake ruptured the ground surface. An image, linked here, shows the location of Spencer Canyon, plus the fault scarp. If a person were to extend a line out to the west from the Spencer Canyon fault scarp, this line would extend into the Seattle, Washington area. But there is more to this story.
A Pacific Northwest Seismic Network page, linked here, states that on "the hogback east of the Columbia...the ridge across the canyon from where the old tram was located," two cracks had opened up in the earth. But there is something to note about what was going on in these cracks on the east side of the Columbia River, which were on the other side of the river from the Spencer Canyon fault. The page notes the following: "Deep down in the earth every five minutes there was an explosion like the shot of a cannon and out of the cracks in the earth a dark fluid was oozing which hardened as it ran down the mountain side and cooled." One of the eyewitness to this event "took some of that dark material and had it analyzed and it was found to be oil."
To help establish where the cracks were in the hogback on the east side of the Columbia River, we must establish the location for the old tram. A page, linked here, contains an important piece of information. It speaks of Waterville, Washington which is located "high on the plateau above the Columbia," at "an elevation of 2,650 feet." The wheat farmers around Waterville needed a way to get their wheat down to ports on the river. In 1902, "the Columbia River Tramway Company began operating trams from the edge of the bluff down the breaks to a steamboat landing three miles north of Orondo." These trams were two miles long and operated until 1910. But, it appears that this tram system stood for quite some time after.
On a map linked here, Waterville, Washington is shown as being located east of Entiat, Washington. So it is evident that the tram being spoken of in the crack-in-the-ground entries is the same tram operated by the Columbia River Tramway Company, which was used to haul wheat down to the river landing and other goods back to the top of the plateau for use in Waterville.
At the bottom of PDF page 5 of 12, on the page linked here, is a map which indicates the apparent route of the old tram. It is directly across the Columbia River from Entiat, Washington. Information about this tram continues onto page 6. Since this tram is across the river from Entiat, Washington, this virtually confirms that this is the tram of which, across the canyon from it, was the hogback on which were those two cracks which opened in the ground during the 1872 earthquake, and spewed forth oil.
A page, linked here, gives more detailed information where the Waterville Wheat Tramway was located. It also notes that at the Rocky Reach Dam visitor center is a display on the history of this tram. Regarding the old tram, the page states: "All that remains is a concrete foundation with anchor bolts to mark the spot." A satellite photo, linked here, marks the "Top of Old Tram" and the "Hogback across from Tram" in relation to the town of Entiat, which is located on the west side of the Columbia River. Once again, the hogback across from the tram is where two cracks opened in the ground during the 1872 earthquake, and oil came out of the ground. Now back to other cracks or fissures which opened in the ground in 1872.
A USGS webpage, linked here, declares: "Most of the ground fissures occurred at the east end of Lake Chelan in the area of the Indian camp; in the Chelan Landing-Chelan Falls area; on a mountain about 19 kilimeters west of the Indian camp area; on the east side of the Columbia River (where three springs formed); and near the top of a ridge on a hogback on the east side of the Columbia River. These fissures formed in several localities of differing physiographic environments." The page also states: "Sulfurous water was emitted from the large fissures that formed in the Indian camp area. At Chelan Falls, 'a great hole opened in the earth' from which water spouted as much as 9 meters in the air. The geyser activity continued for several days, and, after diminishing, left permanent springs."
The USGS page, linked above, contains another piece of valuable information. It states: "Damaging intensities in Washington (MM intensity VI) extended on the west throughout the now densely populated Puget Sound basin and on the southeast to beyond the Hanford nuclear reactor site. The earthquake also was reported in Idaho, Montana, Oregon, and Canada. Many aftershocks were observed in the area over the next 2 years." Because of its great importance to our future, please note once again that "damaging intensities in Washington (MM intensity VI) extended on the west throughout the now densely populated Puget Sound basin and on the southeast to beyond the Hanford nuclear reactor site." As a cautionary note, it appears that Hanford Nuclear Reservation, with all of its highly radioactive units, could be seriously impacted if another one of these quakes occurred.
It is now time for some final considerations. The earthquake of 1872 opened cracks and fissures on both sides of the Cascade Mountains. On the east side of the Cascade Mountain, the area affected with ground cracking stretched from Chelan, in the north, to Entiat, in the south. On the west side of the Cascades, there was ground cracking on the south side of Seattle. A satellite photo, linked here, has Chelan and Entiat marked, on the east side of the Cascades, and Seattle marked on the west side. At this point, there is an important statement to make. Because of the cracking on both sides of the Cascade Mountains, and because the cracking took place in a relatively wide band on the east side of the mountains, it appears that the massive earthquake of 1872 was located on one of the much deeper fault networks which pass beneath the Cascades. These networks below the Cascades join fault systems on the west side to those on the east side of the mountain range.
The "interconnected [fault] system underlying the Cascades, from Puget Sound" to the east side of the Cascades, at least in the Hanford region, is noted in a webpage linked here. Another page which includes similar information about fault systems which pass under the Cascade Mountains is linked here.
In closing, there is one item on the Internet which could be of interest to this discussion. A page from the Montana Department of Transportation, linked here, in the left hand column (zoom in), speaks about "the Lewis and Clark Fault Zone, as series of faults that stretch between northwest Washington State and the Helena [Montana] area." If this fault zone stretches all the way to northwest Washington, then it would be reasonable to believe that it passes under the Cascade Mountains, somewhere in the region where the massive earthquake of 1872 occurred.
For further reading:
The Day the Earth Shook
http://www.inlander.com/spokane/the-day-the-earth-shook/Content?oid=2179535
Current Expectations for a Cascadia Mega-Quake
https://cascadian.neocities.org/cascadiaquake.htm
No comments:
Post a Comment