Tuesday, November 25, 2014

Week 11: Geologic Processes on the Surface

Mount Timpanogos seems to reign over the Utah and Heber Valleys. It rises up to the east of my Pleasant Grove home. Ice glaciers formed and molded the mountain until very recently. Glacial activity caused its many sharp edges and u-shaped amphitheaters. In 1994, a large crevasse opened up, showing that under the rock debris from physical weathering (talus), there is still a glacier.

 Battle Creek, found in Battlecreek Canyon, east of Pleasant Grove, has been carving out its canyon for millions of years. Evidence of erosion (aside from the canyon, itself, which you can see in the left center of the above picture of Mt. Timpanogos) include the slopes up on either side of the creek and the meanders found in the creek's path.
The many large rocks found in the Battle Creek indicate to me that the water from the creek has loosened parts of the mountain further up and the rocks have rolled down into the creek bed.
 Beneath the large rocks are smaller rocks and beneath those, fine soil. Because the creek has seasons when it is dry and seasons when it is wet, depending on the time of year, this has given the sediment a chance to settle into all the cracks in and around the larger rocks.

Monday, November 17, 2014

Week 10: Earthquakes in Utah

The closest faults to my home in Pleasant Grove are:
1.  Wasatch Fault, Provo Section
2.  Utah Lake Faults
3.  Southern Oquirrh Mountain Faults

In the past week, a few seismic events have occurred near my home. One was a 2.1 magnitude earthquake northeast of Morgan on November 10 at 7:25 PM*. Another earthquake, magnitude 1.2, hit Morgan itself on November 13 at 9:37 AM. More recently, a magnitude 2.1 earthquake occurred in Goshen on November 15 at 7:43 PM.

Utah is seismically active because it is the transition between the thinner Basin and Range Province to the west and the thicker Rocky Mountain and Colorado Plateau Provinces. For at least 15 million years, the crust under this transition zone has been stretched. Faults move when built-up stress is suddenly released and blocks of the earth's crust slide against each other.

The most important things for my students to know about earthquakes:

1.  In the past 150 years, Utah has experienced about 15 earthquakes magnitude 5.5 and above.
2.  Urban areas near the Wasatch Fault are at the most risk for an earthquake.
3.  Earthquakes can also cause other damage, such as fires or leakage of hazardous materials.
4.  Have a disaster plan in place with your family--what to do during an earthquake. (Drop, Cover, and Hold on!)
5.  Have a plan with your family for what do to after the earthquake, e.g. where to meet if separated.
6.  Have emergency materials both in your home and in your car.
7.  Along with emergency materials, keep some emergency money in the form of small bills.
8.  Be aware of hazards in your home, such as heavy wall hangings, mirrors, and pottery that could       fall on someone. Imagine the scene at six o'clock on "Mary Poppins."
9.  Older homes, schools, and workplaces may need to be retrofitted.
10. Once you are prepared, sit back and relax. You have done everything you can, now live your life and don't worry about the "Big One" until it comes.

*In the time between when I wrote this and when I downloaded the pictures, this earthquake disappeared from the map, as it was more than a week since its occurrence.

Sunday, November 9, 2014

Week 9: Geologic Time

I live in Pleasant Grove, which has seen many changes since the Paleozoic Era hundreds of millions of years ago.

In Paleozoic times, Pleasant Grove was under the water of the Paleo-Ocean. It was close to the shore, and covered by shallow water. The sediment deposited there was most likely well-washed quartz sand.    

In the Early Jurassic period, Pleasant Grove was cut off by the moisture of the ocean by the mountains that were rising in the west. Desert sands blew into Utah from the north and northwest. These sands formed dunes that eventually formed sandstone.    

During the Late Jurassic period, dinosaurs roamed the earth near Pleasant Grove. Utah was a swampy lowland. Volcanoes began forming mountains nearby.    

During the Late Cretaceous period, Pleasant Grove was located near one of many rivers flowing towards the Inland Sea. Dinosaurs continued to roam. The Pacific Plate collided with the continent and produced high mountains.    

During the Paleocene era, the high mountains around Pleasant Grove eroded. Sediments filled the inland sea and the rivers that flowed into it. The pressure from the Pacific Plate pushed the land nearby up into a plateau.    

During the Eocene Era, the mountains around Pleasant Grove eroded to almost nothing. The ground itself continued to rise in elevation from the pressure of the Pacific Plate. Organic matter produced fossils and oil shales. 

In the Oligocene Era, Pleasant Grove continued to rise, while rivers started carving through the elevated plateau. Plains and mountains surrounded the area. As extension began, volcanic activity started to occur.    

In the Miocene Era, Pleasant Grove continued to rise and tilt northeastward. It was covered by a lake, formed by the extension as two plates pulled apart. Volcanic activity continued nearby.    

During the Pleistocene Era, Pleasant Grove was completely covered by Lake Bonneville. The climate was colder and glacial activity took place. Battlecreek and Grove Creek Canyons were carved out by rivers.    

Presently, Pleasant Grove is at the foot of the Wasatch Mountains. These mountains were formed by plates pushing together and by glaciers. Also near Pleasant Grove is Utah Lake, one of the last remaining parts of the great Lake Bonneville. 

Pleasant Grove has seen an incredible amount of geologic activity since the Paleozoic Era. From being the shore of the western ocean, to desert, to swamp, to volcanic activity, to plateau, to the bottom of a great freshwater lake, and finally to the base of a great mountain range. This assignment has made me wonder: Is there a better place in all the world than to study geology than Utah? What a wonderful, diverse geologic state we live in.


Monday, November 3, 2014

Week 8: Rock Structures

 This picture was taken from I-15 of the mountains just east of Willard, Utah. One interesting feature of these mountains is the band of lighter-colored rock that is in the top middle of them. I believe this is the result of thrust faults. This seems to be the result of a footwall that has folded over the hanging wall. The evidence for this is that you can see the layers in a rippling pattern, and erosion has revealed the different-colored layers at the top of the fold.

This picture was taken from Highway 89 in Brigham City. You can see in the mountains to the east the distinct thrust fault. The footwall is above, where the "I" is, and the hanging walls are below.This is the result of compressional stress. As the plates push together, the top plate folds over the bottom plate, causing steep folds.