Tuesday, October 28, 2014

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.

Tuesday, October 21, 2014

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: 
Coordinates38°41′00″N 109°34′00″W

Tuesday, October 14, 2014

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.

Tuesday, October 7, 2014

Week 4: Impact of Minerals




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).