USGS/Cascades Volcano Observatory, Vancouver, Washington
DESCRIPTION:
Amboy Crater, California
Amboy Lava Field, California
- Amboy Lava Field
- National Natural Landmark
Compiled From:
1
Smithsonian Institution - Global Volcanism Program, 1999,
2
Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.243-245,
Contribution by Ronald Greeley.
-
Amboy Crater and Lava Field
Location: California
Latitude: 34.55 N
Longitude: 115.78 W
Height: 288 meters (945 feet)
Type:
Cinder Cone1
and
Monogenetic volcanic field2
Eruptive History:
Holocene ?2
From:
Miller, 1989,
Potential Hazards from Future Eruptions in California:
USGS Bulletin 1847
-
Amboy Crater - Lavic Lake Basalt Fields
-
- erupted approximately 10,000 years ago;
- consists of several mafic lava flows and cinder cones from several vents
during the past approximately 10,000 years;
- volcanic domes: none recognized;
- mafic tephra erupted at several vents during the past approximate 10,000
years;
- pyroclastic flows: none recognized;
- blasts and pyroclastic surges: none recognized;
- debris avalanches and debris flows: none recognized;
- most recent eruption: mafic cinder cones and lava flows of apparent
Holocene age (approximately 10,000 years ago);
- most probably future potential hazard (based on consideration of size,
frequency, and severity of event):
formation of cinder cones, small volumes of tephra, and lava flows;
phreatic explosions.
From:
Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.243-245,
Contribution by Ronald Greeley
-
The Amboy lava field covers approximately 70 square kilometers and
consists primarily of
vesicular pahoehoe.
The field is in an alluvial-filled valley between the
Bullion Mountains to the southwest and the Bristol Mountains to
the northeast. Within the valley, it lies between Bagdad Dry Lake to the
west and Bristol Dry Lake to the east; both are playa lakes typical of
the Mojave Desert.
-
Amboy Crater is a prominent, undissected
cinder cone
in the northeastern quadrant of the lava field. The volcano erupted along the
northern border of Bristol Dry Lake and poured lava onto its surface, dividing
it into the two present playas. The cone rises 75 meters above the surrounding
lava flows and is approximately 460 meters in basal diameter. It is composed of
a loose accumulation of volcanic ejecta with secondary amounts of agglutinated
scoriaceous tephra plus ropy, ribbon- and almond-shaped bombs. Some lithic
non-vesicular accessory basaltic ejecta are present, but included xenolithic
fragments are absent.
-
Amboy Crater is not a single cone but is composed of at least four nearby
coaxial nested cones. The outher slopes of the main cone are gullied by
erosion. Within the main outer cone, there is a remnant of a second cone on the
west side; both cones are breached on the west. In addition to the two main
cones, there are two relatively undisturbed cone walls within the main crater.
These innermost cones are composed almost entirely of angular scoriaceous
cinders.
-
Most of the Amboy lava field is composed of undifferentiated flow units
of relatively dense, "degassed" pahoehoe lavas that form a hummocky terrain.
The surface relief on this unit ranges from 2 to 5 meters. The flow is
characterized by abundant tumuli and pressure ridges and, as is typical for this
type of flow, a fractured surface.
Lava tubes
are not present in any of the flows, nor are blisters or shelly-type pahoehoe;
only a few lava channels are present. Low-lying areas on the flow are filled
with windblown sediments which range from a few centimeters to more than 1 meter
thick. The thickness of aeolian deposits increases towa the southwest part of
the field. Sand-blasting is prevalent over the entire flow, and wind-faceted
pebbles of basalt are common.
-
The oldest flows occur in the eastern and southeastern part of the field. They
are characterized by numerous collapse depressions up to about 10 meters in
diameter and several meters deep. Although the name would imply that "collapse"
depressions formed by the collapse of a crust over fluid lava, at least some
depressions may form as a result of inflation of an emplaced, but still
plastic, crust by molten lava around a general void in the flow.
National Natural Landmark
|
-- U.S. National Park Service, National Natural Landmarks Website, 2003
-
Amboy Crater:
San Bernardino County - Excellent example of a recent
volcanic cinder cone with an unusually flat crater floor.
Owner: Federal, Private (May 1973). Designation Date: May 1973.
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03/19/07, Lyn Topinka