Bonito Lava Flow
The Bonito Lava flow is a basaltic Aa flow (see
Sunset Crater Nature Trail Earthcache for longer description of
Aa flows). It ranges in thickness from 5 feet at the edge to over
100 feet in the center. As this lava flowed out from the base of
Sunset Crater Volcano, it had a lot of gas still dissolved in it.
As the gas came out of solution, just like the carbon dioxide in
carbonated drinks, it formed bubbles in the lava. Some of these
bubbles were frozen in the lava in what are called vesicles. Most
of the vesicles are small, but sometimes, the gas accumulates under
outer surface of the flow that has cooled forming large
vesicles.
These large vesicles can be seen throughout the
Bonito Lava Flow. As part of the logging requirement, count the
number of large vesicles you can see from the coordinates.
Lava Dome
Sunset Crater Volcano is a type of volcano called a cinder cone
(see
Sunset Crater Nature Trail Earthcache for that process).
Looking north across the Bonito Lava Flow another type of volcano,
a lava dome can be seen. Both O’Leary Peak and Darton Dome
are lava domes. Lava domes are formed from lava that is viscous,
meaning it doesn’t flow easily. As a result the lava mounds
up right by the vent forming a rounded steep sided dome.
Logging requirements:
Send the cache owner a note (click on "A Cache by TerryDad2 and
adopted by Jeep_Dog" link) with :
- The text "GCZ5H1 Bonito Lava Flow" on the first line
- The number of people in your group.
- Send me a note with the number of large vesicles you can count
from the coordinates
- Request, but not a requirement (and can be helpful if any
answers for above question are incorrect): for additional
verification to avoid armchair logs, please include with your
online log a photo of your group with GPS at the cache
location.
The above information was compiled from the following
sources:
- National Park Service, 2005, Lava Flow Trail,
Trail Guide, Sunset Crater Volcano National Monument.
- USGS, 2005, Geology of Sunset Crater National
Monument, How about going on a volcanic field trip?
http://wrgis.wr.usgs.gov/parks/sunset/sunsetft.html
- Hanson, Sarah L. 2003, Roadside Geology: :
Wupatki and Sunset Crater Volcano National Monuments, Arizona
Geological Survey, Down-to-Earth 15
- National Park Service, Sunset Crater Volcano
National Monument, Geologic Resource Evaluation.
- Holm, Richard F, and Richard B. Moore, 1987,
Holocene scoria cone and lava flows at Sunset Crater, northern
Arizona, in Geological Society of America Centennial Field Guide
– Rocky Mountain Section, 1987.
Placement approved by the
Sunset Crater National Monument