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.

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.

   

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.

Week 7: Metamorphic Rocks

Metamorphic rocks occur in the canyons nearby my home. As I hike through Battle Creek Canyon, just East of Pleasant Grove, I see slate everywhere. This indicates that shale has been exposed to low-grade metamorphism. The convergent plate boundary nearby must have caused regional metamorphism to occur below the surface. Through millions of years of erosion from water and wind, this metamorphic rock is not accessible.

Slate, a metamorphic rock, is commonly used for floor and roof tiles, because it has parallel lines of weakness that make it easy to split into smooth slabs. Marble is also used as a high-class addition to many homes, commonly as bathroom tile and countertops and columns. As evidenced below, metamorphic rocks are also commonly used as gravestones.

This gravestone appears to be made of a kind of migmatite--igneous and metamorphic rock mixed. You can tell by the dark and light pods and layers.

This gravestone appears to be made of marble, a rock made of metamorphosed limestone.

This gravestone is another that appears to be made of marble.

The three gravestones above were found at the Pleasant Grove Cemetery, located at 100 East 400 South in Pleasant Grove.

Week 6: Sedimentary Rocks

Arches National Park is a unique treasure that is just a few hundred miles away from us. It is the densest collection of natural stone arches in the world. 

Arches is made up of two main formations--Entrada and Carmel (or Navajo). The Entrada layer is porous sandstone, formed by a vast desert. The Carmel layer beneath is comprised of a mix of sand and clay, formed by desert-like conditions about 210 million years ago. It is more dense than the Entrada layer, which was formed by stream laid and windblown sediments about 140 million years ago.. 

Deep beneath is a layer of salt deposited in the Paradox Basic 300 million years ago. This salt has squeezed upwards, cracking large domes into the layers above. Rain water drains into the porous Entrada layer and dissolves the calcite that makes up the sandstone of both layers. During the winter, the water freezes and expands, causing more cracking and erosion from the inside.

Most of the formations visible at Arches National Park are the salmon-colored Entrada formation or the buff-colored Carmel formation. 

My little family visited the Double Arch last summer.

Arches National Park is located at: 

Coordinates	38°41′00″N 109°34′00″W

Week 5: Igneous Rocks

Igneous rocks are surprisingly common in Utah. The most common is granite, which is found throughout the state. Granite is an in extrusive rock, meaning that it is formed deep within the earth, and the magma forming it has cooled slowly, allowing large crystals to form. After many millennia of erosion, the rock that was once deep below the surface is now quite near the surface and available for mining. As a result, many historic buildings in the state are made of or contain granite. Granite is used commonly for countertops in homes and for educational and commercial buildings. 

The interior of the Utah County Courthouse (151 South University Avenue, Provo) has granite facing. The stone came from Little Cottonwood Canyon and is similar to the granite used to build the Salt Lake Temple.

The Tanner Building on BYU campus (490 Tanner Building, Provo) is also made of granite. 

Early Native Americans used obsidian (a glassy, intrusive igneous rock) that they found and mined for arrowheads and for trading.

Week 4: Impact of Minerals

Sapphire

Graphite

Aluminum.

Sapphire, graphite, and aluminum are minerals. This means that they form naturally on the earth and have a specific composition and structure. All of these minerals are found at my home and are used often. 

Aluminum (or aluminium, if you are a Brit) is an element, a metal, and a mineral. It is actually the most common metal in Earth's crust. The element itself is formed in supernovae, but the mineral aluminum is most often found in bauxite (not a mineral itself, but a combination of minerals, or a rock). Bauxite is formed when the silica in aluminum-containing rocks is washed away. Deposits of bauxite are found as flat layers close to the earth's surface and can extend for miles. It is typically mined by bulldozers digging to the bauxite layer and explosives that bring the ore to the surface. The bauxite layers are then taken to a processing plant. Through a series of chemical reactions, the aluminum is separated into aluminum oxide, a fine white powder also called alumina. Alumina is then smelted into aluminum, which is very versatile and can be formed into sheets (pictured above), rods, and thin wires. Other uses for aluminum are transportation (cars, airplanes, trucks, and railroad cars) and packing (cans).