Geology Introduction to Lassen and Warner Valley Webcourse Click through the presentation before the...
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Transcript of Geology Introduction to Lassen and Warner Valley Webcourse Click through the presentation before the...
Geology Introduction to Lassen and Warner Valley
WebcourseClick through the presentation before
the fieldtrip to Warner Valley.
As you may know, the Earth can be categorized into three layers: the crust, mantle, and core.
crust
mantle
core
We live on the crust
The Earth’s crust is composed of tectonic plates that float on and move around relative to the underlying mantle.
Press and Siever, 1998
Where plates collide, you have convergent boundaries
Press and Siever, 1998
Where plates move apart, you have divergent boundaries
Press and Siever, 1998
At each of these margins you get volcanism!
Press and Siever, 1998
You can also get volcanism in the middle of plates… like in Hawaii.. but that is a story for another day.
Press and Siever, 1998
We are going to focus on the volcanism that occurs at a convergent margin where an oceanic plate is subducting beneath a continental plate.
Press and Siever, 1998
Subducting means one plate is
going underneath another,
like right here
This type of volcanism is what formed the Cascade Mountain Range and the volcanoes at Lassen Volcanic National Park.
Lasse
n isway
down here!
Magma formation at subduction driven volcanoes looks something like this.
modified from S. Rost, 2008
Lassen Volcanic National Park has several volcanoes, which include:
Lassen Peak
Chaos Crags
Mount Tehama
(Brokeoff Mountain)
And the remains of ancient Mt. Tehama,
which erupted violently approximately 350,000 years ago, leaving only a collapse crater.
crater rim‘caldera’
Estimation of Mt Tehama
Mapview of caldera rim
Today, Lassen exhibits another feature of volcanic regions: an active hydrothermal system.
Hotspring at Devil’s Kitchen
Devil’s Kitchenhydrothermal areais this way
Bumpass Hellhydrothermal area
Little Hot Spring Creek
Sulphur WorksHot Springs
The hydrothermal system is visible on the surface in the form of hot springs and fumaroles
Hot spring:area where hot water emerges from the Earth
Fumarole:vent thru which hot gases escape
Hydrothermal systems form in parts of the Earth’s crust where there is water and heat.
precipitation(rain, snow)
streams
groundwater
magma
magmatic heat
Springs, fumaroles
water
heat
At Lassen, the heat comes from the magma stored deep beneath the volcano,
precipitation(rain, snow)
streams
groundwater
magma
magmatic heat
Springs, fumaroles
water
heat
and the water comes from rain and snowmelt that infiltrates into the soil and underlying crust.
precipitation(rain, snow)
streams
groundwater
magma
magmatic heat
Springs, fumaroles
water
heat
precipitation(rain, snow)
magma degassing
streams
groundwater
magma
HydrothermalCirculation
magmatic heat &
H2O, CO2, HCl, H2Svolatiles:
Springs, fumaroles
water
heat
In addition to picking up heat, the circulating groundwater picks up volcanic volatiles that have escaped the magma.
volatiles
Fe
Fe
Fe
Fe
Si
Si
Si
ACID
IC W
ATER
This volatile-rich water reacts with crustal rocks as it rises to the surface in the hydrothermal circulation zone.
The chemical and physical properties of the heated water and volcanic volatiles results in the hydrothermal features we see around Lassen.
Hydrothermal areas are located in three main areas:
Inside the ancient caldera
South of the park
Warner Valley
In the Lassen Astrobiology Intern Program, we’re going to be working in Warner Valley.
Warner Valley
Warner Valley
Lake AlmanorView of Warner Valley to the southeast from above Lassen Peak.
Lassen Peak
Bumpass Hell
Warner Valley
Map-view of Warner Valley
And although it is not clear from satellite imagery, when we overlay a geologic map…
Warner Valley
we can see what rock is exposed on the Earth’s surface in this area.
Warner Valley
We can see that Lassen and Warner Valley are composed of different geologic units.
Each of these colors represents a different unit
Warner Valley
Each of these geologic units are composed of a rock of a particular relative age and chemical composition.
Each of these colors represents a different unit
Warner Valley
Basalt/Basaltic Andesites(Sifford Mtn.) Andesites
(Dittmar Volcanic Ctr.)
Andesites (Dittmar Volcanic Ctr.)
Dacite (Flatiron Ridge)
Dacite (Panther Creek)
Dacite (Bumpass Mtn.)
Warner Valley field area
Dacite (Bench Lake)
glacial till
Around Warner Valley, there are a variety of volcanic rocks and glacial sediments.
Basalt/Basaltic Andesites(Sifford Mtn.) Andesites
(Dittmar Volcanic Ctr.)
Andesites (Dittmar Volcanic Ctr.)
Dacite (Flatiron Ridge)
Dacite (Panther Creek)
Dacite (Bumpass Mtn.)
Warner Valley field area
Dacite (Bench Lake)
glacial till
The names dacite, andesite, and basalt, describe volcanic rocks of a particular chemical composition and grain size.
Basalt/Basaltic Andesites(Sifford Mtn.) Andesites
(Dittmar Volcanic Ctr.)
Andesites (Dittmar Volcanic Ctr.)
Dacite (Flatiron Ridge)
Dacite (Panther Creek)
Dacite (Bumpass Mtn.)
Warner Valley field area
Dacite (Bench Lake)
glacial till
The white ‘glacial till’ units indicate areas filled with sediment deposited by glaciers.
We will be visiting several sites in Warner Valley on our fieldtrip.
Warner Valley Campground
SpringsDevil’s Kitchen
This map tells us more than just rock type, it also indicates:
faults
topographycreekshot springs
elevation
We will be using this type of map in the field to locate where we are and determine additional information about our fieldsites, utilizing work done by scientists before us.
Now for a few Questions:
• Can you locate the Warner Valley Campground, Drakesbad, and Devil’s Kitchen on Google Maps?
• In what geologic units are our fieldsites?
• *Bonus* What geologic units might exist beneath the surface deposits at our fieldsites in Warner Valley?