Formation of the Three Types of Rocks and Famous Rock Formations

Sedimentary Rocks

The materials of which the Earth’s crust is composed are rocks. Rocks are naturally occurring

materials, themselves composed of combinations of minerals. Few rocks are composed of a single mineral.

Rocks are classified by where and how they are formed.

All rock types can be physically and chemically broken down by a variety of surface processes

collectively known as weathering. The sediment that is created by weathering is often moved through the

landscape by erosional forces such as streams, glaciers, wind, and gravity. When this debris is deposited as

permanent sediment, the processes of burial, compression, and chemical alteration can modify these materials

over long periods of time to produce sedimentary rocks. These rocks have been exposed to weathering on

the Earth’s surface. Most sedimentary rock has formed on the sea bed; as layer upon layer of sediment is

deposited one upon another, the weight of the continuous deposits squeezes out water and causes chemical

changes in the minerals present. These changes can cause the grains to become cemented together and new

sedimentary rock is formed. Distinct layers, depicting different periods of deposition can usually be found in

sedimentary rock. (Examples: Sandstone, Shale, Conglomerate, Limestone, Chert, Coal, Gypsum). The

following examples are famous sedimentary rocks.

The Grand Canyon is probably one of the most famous sedimentary rock formations.

The most powerful force to have an impact on the Grand Canyon is erosion, primarily by water (and ice) and second by wind. Other forces that contributed to the Canyon's formation are the course of the Colorado River itself, vulcanism, continental drift and slight variations in the earth’s orbit which in turn causes variations in seasons and climate.

Water seems to have had the most impact basically because our planet has lots of it and it is always on the move. Many people cannot understand how water can have such a profound impact considering that the Canyon is basically located in a desert. This is one of the biggest reasons that water has such a big impact here. Because the soil in the Grand Canyon is baked by the sun it tends to become very hard and cannot absorb water when the rains to come. When it does rain the water tends to come down in torrents which only adds to the problem. The plants that grow in the Grand Canyon tend to have very shallow root systems so that they can grab as much water as possible on those rare occasions when it does rain. Unfortunately, these root systems do nothing to deter erosion by holding the soil in place. Now you've got lots of water, no place for it to go, but down to the Colorado River, and nothing holding the soil and rock in place. The result is frequently a

flash flood roaring down a side canyon that can move boulders the size of automobiles, buses and even small houses. If automobiles, buses and small houses are in the way then it will take them too. Luckily no one builds houses in the Grand Canyon so that's not a problem but there are a few autos, vans and buses sitting at the bottom of the Colorado. This mass that moves down a side canyon during a flash flood is more like a fast- flowing concrete than water and it can be very dangerous. You should always be well informed of weather conditions when you are hiking through side canyons in the Grand Canyon.

Rocky Hoodoos are tall skinny spires of rock that protrude from the bottom of arid basins and "broken" lands. Hoodoos are most commonly found in the High Plateaus region of the Colorado Plateau and in the Badlands regions of the Northern Great Plains. While hoodoos are scattered throughout these areas, nowhere in the world are they as abundant as in the northern section of Bryce Canyon National Park. In common usage, the difference between Hoodoos and

pinnacles or spires is that hoodoos have a variable thickness often described as having a "totem pole-shaped body." A spire, on the other hand, has a smoother profile or uniform thickness that tapers from the ground upward.

At Bryce Canyon, hoodoos range in size from that of an average human to heights exceeding a 10-story building. Formed in sedimentary rock, hoodoo shapes are affected by the erosional patterns of alternating hard and softer rock layers. The name given to the rock layer that forms hoodoos at Bryce Canyon is the Claron Formation. This layer has several rock types including siltstones and mudstones but is predominantly limestone. Thirty to 40 million years ago this rock was "born" in an ancient lake that covered much of Western Utah. Minerals deposited within different rock types cause hoodoos to have different colors throughout their height.

Formational Process:Hoodoos are formed by two weathering processes that continuously work together in eroding the edges of the Paunsaugunt Plateau. The primary weathering force at Bryce Canyon is frost wedging. Here we experience over 200 freeze/thaw cycles each year. In the winter, melting snow, in the form of water, seeps into the cracks and freezes at night. When water freezes it expands by almost 10%, bit by bit prying open cracks, making them ever wider in the same way a pothole forms in a paved road.

Igneous Rocks

Igneous rocks have been formed by cooling and crystallization of molten rock (magma). The magma

could have been formed in the crust or upper mantle of the Earth. It consists of molten silicates, water, and

gases. Magna tends to rise into and through the crust since it is less dense than solid rock. Igneous rock can

been identified by its crystals which are often large enough to be seen with the naked eye. The size of the

crystals depends upon the rate at which the magma cools: rapid cooling such as magma that rose quickly to

Earth’s surface, results in very small crystals. Large

crystals form when the magma cools slowly and

solidifies before reaching the surface. (Examples:

Granite, Obsidian, Basalt, Pumice, Andesite, Diorite,

Rhyolite). The following are examples of famous

igneous rock formations.

Mount Rushmore National Memorial is located along the northeast edge of what is known as the Harney Peak Granite Batholith in the Black Hills of South Dakota. A batholith is a geologic feature that formed by the cooling of a large igneous body of magma below the earth's surface; if a similar igneous body reaches the earth's surface, it would form a volcanic feature such as a lava flow. The Black Hills magma was emplaced into the older "host" mica schist rocks during Precambrian time, approximately 1.7 billion years ago! The mica schist originated from the metamorphism (alteration by heat and pressure) of muds and sands from an ancient sea floor sometime prior to the emplacement of the Harney Peak Granite. Metamorphism of this original material produced the "slabby" appearance in the mica schist that now contains minerals such as muscovite, biotite and quartz. The Harney Peak Granite (of which Mount Rushmore is carved) consists of fine-grained minerals including quartz, feldspar, muscovite and biotite. It is believed that these minerals formed approximately 8 miles below the earth's surface from molten magma. Some cracks developed as a result of the cooling of the magma and were later "patched" with molten magma. The result was the emplacement of pegmatite dikes that filled the fractures and zones of weakness in the granite. Today these pegmatite dikes are expressed as white streaks on the foreheads of Presidents Washington and Lincoln. Elsewhere in the Black Hills, economically significant mineral deposits are found associated with these pegmatite bodies. The Harney Peak granite was likely exposed at the surface prior to Cambrian time, but was covered by sandy sediment when the Cambrian seas invaded the Black Hills some 550 million years ago. Today, these sands are part of the Deadwood Formation sandstones that contain grains derived from the ancient Harney Peak granite and the exposed Precambrian surface. The granite core of the Black Hills continued to be further buried during the rest of the Paleozoic and Mesozoic eras of geologic time and wasn't exposed to surface processes again until some 50 million years ago when today's Black Hills began to take on their present form.

Stone Mountain as a natural wonderFrom the point of view of nature, Stone Mountain, itself, is wondrous, boasting the following statistics:

1. It’s the world’s largest piece of exposed granite.

2. It’s counted as one of Georgia’s seven natural wonders.

3. It’s an 825-foot tall dome-shaped, isolated mountain (the scientific term is “monadnock“) made of granite.

4. It rises 1,683 feet above sea level.5. It covers 583 acres.6. It has a base circumference of 3.8 miles.7. It covers 583 acres.8. It was created 300 million years ago by a pocket of magma trapped underground.9. It rose to the earth’s surface 15 million years ago as a result of uplift and erosion.10.From the top of the mountain, on a clear, winter day, you can see more than 45 miles.

Metamorphic Rocks

A number of geologic processes, like tectonic folding and faulting, can exert heat and pressure on both

igneous and sedimentary rocks causing them to be altered physically or chemically. Rocks modified in this way

are termed metamorphic rocks. Metamorphic rock has undergone physical and/or chemical changes when

existing rock (sedimentary, igneous or metamorphic) becomes buried because of Earth movements. The rock

will undergo extreme pressure and if buried deeply enough, will become heated and a new rock will form.

Baked rock does not melt, but it does change. It forms crystals. If it has crystals already, it may form larger

crystals. Metamorphosis can occur in rock when they are heated to 300 to 700 degrees Celsius. (Examples:

Marble and Quartzite). The following examples are famous metamorphic rock formations.

The Taj Mahal (Persian for Crown of Palaces) is an ivory-white marble mausoleum on the south bank of the Yamuna river in the Indian city of Agra. In 2007, it was declared a winner of the New7Wonders of the World (2000–2007) initiative.

It was commissioned in 1632 by the Mughal emperor, Shah Jahan (reigned 1628–1658), to house the tomb of his favorite wife, Mumtaz Mahal. The tomb is the centrepiece of a 42-acre complex, which includes a mosque and a guest house, and is set in formal gardens bounded on three sides by a crenellated wall.

A Special Case

The Himalayan range, topped by 29,035-foot (8,850-meter) Mount Everest, the highest mountain in the world, is one of the largest and most distinct geographic features on the earth's surface. The range, running northwest to southeast, stretches 1,400 miles (2,300 kilometers); varies between 140 miles and 200 miles wide; crosses or abuts five countries-India, Nepal, Pakistan, Bhutan, and People's Republic of China; is the mother of three major rivers--Indus, Ganges, and Tsampo-Bramhaputra rivers; and boasts over 100 mountains higher than 23,600 feet (7,200 meters)--all higher than any mountains on the other six continents.

Mount Everest's Geology is Simple

The geology of Mount Everest is very simple. The mountain is a huge slice of solidified sediments that once lay at the bottom of the Tethys Sea, an open waterway that existed between the Indian sub-continent and Asia over 400 million years ago. The sedimentary rock was slightly metamorphosed from its original deposition and then lifted upward at an amazingly speedy rate--as much as 4.5 inches (10 centimeters) a year as the Himalayas rose.