Question

Hi! I have some geology ?'s:

23. To account for the incredible distances traveled by some of the Columbia River Flood Basalts to reach the Pacific Coast, possible explanations include which of the following (more than one answer is recommended):

A. the pre-existing uniform gradual slope toward the Pacific Coast all across Oregon and Washington from their eastern borders to the ocean.

B. the initial high temperature of the lava from these eruptions.

C. the low viscosity of the lava from these eruptions.

D. the filling in of low topography by early flows, flattening the landscape for later flows.

E. solidifying and crusting over of the upper surface of flows, providing insulation to maintain high temperature and low viscosity of flows over great distances.

F. volcanic vents providing freshly erupting lava all along the Columbia River to the ocean.

G. the Oregon coast was much further east at the time of these eruptions, making the journey actually far shorter than it appears today.

24. The methods of monitoring used by USGS volcanologists to accurately predict the 1991 eruption of Mt Pinatubo in the Philippines and save thousands of lives included which of these:

A. seismometers revealing subterranean magma movements


B. sonar measuring tectonic ground movements


C. GPS to figure out where they actually were

D. watching snakes, frogs, chickens, and pigs


E. visual monitoring by flyovers to inspect lava effusions


F. gas spectrometers to measure volcanic de-gassing

G. satellite data to detect thermal anomalies

Answer 1

23. A. the pre-existing uniform gradual slope toward the Pacific Coast all across Oregon and Washington from their eastern borders to the ocean.

B. The initial high temperature viscosity of the lava from these eruptions

C. The low viscosity of lavas from these eruptions

D. The filling in of low topography by early flows, flattening the landscape for later flows.

E. solidifying and crusting over of the upper surface of flows, providing insulation to maintain high temperature and low viscosity of flows over great distances.

Basalt lavas generally have lower viscosities and higher temperature that allow them to travel larger distances than rhyolitic flows. The lavas cool and form a crust, while the core of the lava still remains liquid, allowing lava to be transported further as long as there is a supply. Once the initial lows of the topography have been filled in, the lava can travel greater distances because of the gradual slope that exists from the eastern borders to the west coast.

24. A. seismometers revealing subterranean magma movements


After a series of small steam explosions were recored on the mountain, USGS scientists in collaboration with scientists from the Phillipines set up seismic monitoring equipment as well as correlation spectrometers (not gas spectrometers) to measure the sulfuric acid emanating from the volcanoes.