Dating historic activity at Oso site shows constant major landslides
customs. since then, It's been says this area has experienced major slides before, But it's unfamiliar how long ago they occurred. University of Washington geologists analyzed woody debris buried in earlier slides and used radiocarbon dating to map the of activity at the site. The findings, revealed online in the journal Geology, Show that a massive nearby slide happened around 500 long ago, And not thousands of rice as some had believed. "We found that that's incorrect in fact, Landslides have been continuing in the recent past,
The study establishes a new method to date all the previous landslides at a particular location. The method shows that the slopes in the neighborhood around Oso have collapsed on average once every 500 years, And at a higher rate of about once every 140 years within the last few 2,000 quite a few years.
LaHusen had not yet begun his graduate studies when he asked about studying the history of geologic activity at the Oso site. in late summer of 2014, The researchers began their work wading along riverbanks to look for preserved branches or trees that may be used to date previous landslides.
"not have considered a large, disastrous landslide, It could uproot living trees which kills them and also encapsulates them in the landslide mass, Duvall considered that. "If you can easily find them in the landslide mass, You can assume that they were killed by the landslide, And thus you can date as soon as landslide occurred,
The team managed to unearth types of wood buried in the Rowan landslide, Just downstream in the Oso site, And the headache Creek landslide, Just upriver within the 2014 slide. Results from several debris samples show that our Rowan landslide, issues five times the size of the Oso slide, occurred just 300 to 694 years ago. The Headache Creek landslide set in a couple hundred years of 6,000 yoa.
Previous UW research had shown a medical history of geologic activity at the Oso site, consists of previous major landslides and a recent small slide at the same slope that collapsed in 2014. But while the positioning of past slides and degree of surface erosion can [-censured-=https://russianwomendate.weebly.com/]dating ukraine ladies[/-censured-] show the order that the older slides happened, It is actually not possible to give a date for the past events.
The new study uses the radiocarbon dates for two slides create a roughness curve to date other events along a 3.7 kilometer (6 kilometer) Stretch of the north fork of the Stillaguamish River. A roughness curve uses just how much surface erosion to establish each slide's age. The two dates put firm [-censured-=https://russiangirldating.wordpress.com/2019/06/19/to-know-if-the-russian-girl-has-a-crush-on-you-see-if-she-has-these-three-signs/]russian singles[/-censured-] limits on the curve, So that other nearby slides can be dated from their roughness characteristics and never have to find material buried inside each mass of soil.
"This is the first time this calibrated surface dating method has been utilized for landslide chronologies, And it seems to work very well, LaHusen talked about. "It can provide some concerning how often these events recur, might be the first step toward a regional risk analysis,
Applying the new way for other locations would require gathering samples for each area, They cautioned, Because each site has its own soil composition and erosion aspects.
It's not known if thez findings for the Oso site's history would apply to other parts of the Stillaguamish River, Duvall menti one d, Or to other areas in Washington state. the study are still studying debris from other locations. But the results do have implications for instant area.
"It suggests that the Oso landslide was not so much of an anomaly, Duvall understood.
She and LaHusen are also employing the UW's M 9 Project, Which is studying hazards from specifications 9 earthquakes along the Cascadia subduction zone. They would like to learn whether landslides across Washington state coincided with past earthquakes, And use simulations of future shaking to predict which places in the state are most susceptible to earthquake triggered landslides.