[ Earthwatchers ] [ Main Menu ]
98235
From: jordan, [DNS_Address]
Subject: earthquake swarm lake Tahoe (NT)
| (NT) |
98240
From: eaamon, [DNS_Address]
Subject: Re: earthquake swarm lake Tahoe (NT)
|
it was not too long ago that some geologist made the determination that Lake Tahoe was a volcano at one time. they stated that so much evidence was covered by erosion it took a while to figure it out. |
98244
From: Sue Iived there 20 yrs, [DNS_Address]
Subject: Re: earthquake swarm lake Tahoe (NT)
|
What about Round Hill, NV? A cinder cone. What about Cave Rock, NV? A lava tube. Sacred to the local indians. |
98256
From: ao, [DNS_Address]
Subject: Pleistocene volcanism and shifting shorelines at Lake Tahoe, Calif..
URL: The evolution of the landscape surrounding Lake Tahoe..
|
In the summer of '93 I tagged along as a friend did three days of concerts up at the Squaw Valley ski lodge, which was cool in that it gave me easy access to and days to wander around the surrounding peaks and consider the geology of the area while listening to his band fill the alpine air.. Having spent my teenaged years a few miles north (in Westwood) I had some reference to the area, but I came more with an eye developed monitoring volcanoes in Hawaii. In other words I understand a little about the Sierra’s geology, but can interpret volcanism a little better. And the most interesting thing to me was two rocks, one granite, and the other a vesicle filled basalt, and this was almost at the peak of the ridge around the Squaw bowl, sitting side by side, that got me wondering..  Above is a geologic map of the area surrounding the lake.. and the abstract of the paper it’s copied from reads.. Abstract In the northwestern Lake Tahoe Basin, Pleistocene basaltic and trachyandesitic lavas form a small volcanic field comprising ∼1 km3 of lava that erupted from seven vents. Most of these lavas erupted subaerially and produced lava flows. However, where they flowed into an early Lake Tahoe (Proto-Tahoe), they produced deltas consisting of hydrovolcanic breccias as well as pillow lavas draped downslope, pillow breccias, hyaloclastites, and mixtures of lava and wet sediments. Consequently, various former shorelines of Proto-Tahoe are marked by subaerial lava flows overlying subaqueous lava deltas. Isolated explosive interactions produced lapilli tuff cones that built upward from vents on the lake floor or grew as littoral cones where subaerial lava flows crossed the shoreline. Six new 40Ar/39Ar ages define three Pleistocene episodes when lava erupted subaerially and flowed into Proto-Tahoe. Three cycles of canyon damming by lava and down- cutting occurred at the outlet of Proto-Tahoe in the Truckee River Canyon. The canyon was dammed at 2.3 Ma by basaltic lavas at Rampart, which raised lake level from ∼1897 m above sea level to 2048 m. The canyon was again dammed at 2.1 Ma by basaltic lavas at the outlet of Proto-Tahoe near Rampart, which raised lake levels from ∼1914 m to 2073 m. And finally, the canyon was again dammed at 0.94 Ma by trachyandesitic lavas at Thunder Cliffs, which raised lake level to 2085 m. Hence, ancient shorelines that are nearly 200 m above the present lake level are documented at 0.94, 2.1, and 2.3 Ma. The present outlet of Lake Tahoe through the Truckee River canyon has been operative for at least 2.3 million years. Even though the three lava dams are now eroded away, the repeated construction (and removal by erosion) of lava dams has diminished the erosion and deepening of the Truckee River Canyon that otherwise would have occurred. Hence, the soft- sediment sill of Lake Tahoe has been protected, which has helped to maintain the great depth of the lake (500 m). The timing of this repetitive volcanic activity raises implications for future volcanic eruptions and their hazards. The lake could be dammed by lava again causing extensive shoreline flooding as its level rose, or rapid dam failure could cause extensive downstream flooding along the Truckee River on its path to Reno. The complete paper is at the link above.. |
Responses:
[98258]
98258
From: eaamon, [DNS_Address]
Subject: Re: Pleistocene volcanism and shifting shorelines at Lake Tahoe,...
|
did note the page was in 2/2018. I remember telling Cal Orey about 20 years ago she was living in a volcano, she laughed. most older research of the subsurface of the lake was just sediment from runoff. it is good they continued research. can't fool people on earthboppin . net thanks for the link ao! |
Responses:
None
98241
From: eaamon, [DNS_Address]
Subject: Re: earthquake swarm lake Tahoe (NT)
|
actually I always figured it was a Caldera similar to Long Valley. I had always wondered if that small island in the middle of Emerald Bay was a volcanic dome since I first saw it 40 years ago. |
Responses:
None
98236
From: EMY1, [DNS_Address]
Subject: Re: earthquake swarm lake Tahoe (NT)
|
I’m noticing that! EMY |
Responses:
None
[ Earthwatchers ] [ Main Menu ]