Skylab image of the Yellowstone Park and surroundings looking north-east ('+' signs are from the camera).
Yellowstone Lake is in the center, the Beartooth mountains are left of center, and the Bighorn
mountains are the arc to the upper left. Bozeman is among the mountains to the lower left. |
|
A Space Shuttle image of the Yellowstone area; north is at about 11:00
(counterclockwise from straight up). Wispy cirrus clouds cast shadows on the ground. The
following images of the geology of the Yellowstone caldera volcano
are annotated onto the center of this frame.
|
Pre-Caldera Eruptions Starting ~ 1.2 million years ago, volcanic activity shifted
from the west to the site of Yellowstone Park with a series of obsidian (or rhyolite) domes
and flows. These eruptions outlined the main ring fracture for the Yellowstone Caldera.
These pre-caldera lavas are exposed rarely, the bright overlays, being mostly buried
under younger rocks. The inferred original extents of these flows are in the pale overlays,
with their inferred vents as stars. From Figure 8 and Plate 1 of
Christiansen (2001). Other similar flows
may not be exposed at all.
|
|
Lava Creek Tuff The major eruption at Yellowstone, 640,000 years ago,
saw >300 cubic kilometers of volcanic ash erupted in just a few days or years. Much of
this ash erupted as ash flows, 'slurries' of volcanic ash fragments in
superheated steam and gas, which solidified to form the to form the Lava Creek
ash-flow tuff. The Lava Creek looks just like
the Huckleberry Ridge tuff. Outcrops of
the Lava Creek are in the
strong color overlays, and its inferred original distribution in the pale overlay.
Loose ash from this eruption must lain thick on the whole area, as
it spread over all of eastern North America (at least).
From Plate 1 of Christiansen (2001).
|
