Glaciovolcanic Deposits at North Sister Volcano, Oregon
Mentor 1
Barry Cameron
Start Date
28-4-2023 12:00 AM
Description
During the Pleistocene, North America was covered by the Laurentide and Cordilleran ice sheets. In the Pacific Northwest, volcanoes still erupted under these conditions, creating unique rocks that today serve as a trove of information about the setting in which they were deposited. This interaction between glacial ice and the erupting volcano creates glaciovolcanic deposits. Coined tuyas, they are recognized by a base composed of basaltic pillow piles, a mid-section composed of fragmental hyaloclastite rocks and distinctive flat tops. As magma is emplaced beneath ice, it is quenched by the melting ice creating pillows with characteristic glass-rich pillow rims and glassy fragments in hyaloclastites. The glassy pillow rims can help determine the thickness of the glacial ice the volcano erupted into. As the volcano erupts into the glacial ice, a potentially habitable meltwater chamber can form, and the glass-rich rim can preserve potential evidence of microbial activity. One place where we can see an abundance of these basalts is the North Sister stratovolcano in Central Oregon. While a regional ice cap was present, the underlying volcanism left thick glaciovolcanic deposits associated with North Sister and its related features Little Brother and the Island Fissure deposits, which will be the focus of this work. Major, minor and select trace elements were analyzed by XRF, while sulfur and chlorine concentrations will be determined by EMP. Water and CO2 content will be determined by FTIR spectroscopy. Critically, water and CO2 concentrations of the glass help to estimate ice thickness at the time of the eruption owing to the pressure-dependence of volatile solubility in magma. Ice thickness estimates aid paleoenvironmental reconstructions during the Pleistocene and inform paleoclimate models. Furthermore, thin sections of the glassy samples will be examined under a petrographic microscope to document any signs of microbial life.
Glaciovolcanic Deposits at North Sister Volcano, Oregon
During the Pleistocene, North America was covered by the Laurentide and Cordilleran ice sheets. In the Pacific Northwest, volcanoes still erupted under these conditions, creating unique rocks that today serve as a trove of information about the setting in which they were deposited. This interaction between glacial ice and the erupting volcano creates glaciovolcanic deposits. Coined tuyas, they are recognized by a base composed of basaltic pillow piles, a mid-section composed of fragmental hyaloclastite rocks and distinctive flat tops. As magma is emplaced beneath ice, it is quenched by the melting ice creating pillows with characteristic glass-rich pillow rims and glassy fragments in hyaloclastites. The glassy pillow rims can help determine the thickness of the glacial ice the volcano erupted into. As the volcano erupts into the glacial ice, a potentially habitable meltwater chamber can form, and the glass-rich rim can preserve potential evidence of microbial activity. One place where we can see an abundance of these basalts is the North Sister stratovolcano in Central Oregon. While a regional ice cap was present, the underlying volcanism left thick glaciovolcanic deposits associated with North Sister and its related features Little Brother and the Island Fissure deposits, which will be the focus of this work. Major, minor and select trace elements were analyzed by XRF, while sulfur and chlorine concentrations will be determined by EMP. Water and CO2 content will be determined by FTIR spectroscopy. Critically, water and CO2 concentrations of the glass help to estimate ice thickness at the time of the eruption owing to the pressure-dependence of volatile solubility in magma. Ice thickness estimates aid paleoenvironmental reconstructions during the Pleistocene and inform paleoclimate models. Furthermore, thin sections of the glassy samples will be examined under a petrographic microscope to document any signs of microbial life.
