SP Crater has been dated by several methods, but the results,
with ages between 5.5 and 73 ka, conflict rather than agree. Paleosecular variation is one technique that
may help us evaluate the date. Because
Earth’s north magnetic pole changes with time, and because the Late Holocene
time period is characterized by rapid secular variations, we can compare the
magnetic direction locked in the rock with the record of this variation to see
if the 5.5 ka date is possible. We can
also check for the time span between the emplacement of two lava flows from the
eruption. Third, we can determine
whether spatter cones were rafted from the vent and rotated on a vertical axis
Colton Crater (also called Crater 160) is a scoria cone that
exploded when magma encountered water.
Paleomagnetism can be used to determine whether spatter layers were
rotated after cooling, and may also be useful in determining the temperatures
of emplacement of the pyroclasts. This
will help us understand the history and timing of eruptive events in this
rather complex scoria cone.
Both projects will involve field work to better define the
problems and to drill oriented cores from the rock. Lab work will involve cutting the samples and
analyzing them at NAU and possibly at other laboratories. Physics classes through electricity and
magnetism (usually toward the end of the first year of physics) will be
Contact Michael Ort for more information.