How is shale formed for kids

Some limestone is made entirely of fossil shells. Shales that are subject to heat and pressure alter into a hard, fissile, metamorphic rock known as slate , which is often used in building construction. Resources "shale". Chambers Dictionary of Science and Technology. Chambers Harrap Publishers Ltd.

Rocks: Materials of the Lithosphere - Summary. Retrieved on Jenson Vanities James Martin Vanities. Design Services What's New? What is Limestone? What is Marble? What is Sandstone? Limestone is made up of calcium carbonate fizzes with acid. This may be shell fragments, mud, or small, round ooliths that form in tropical lagoons. Chalk is a soft white limestone made from the microscopic skeletons of marine plankton.

More to click Who Runs the Business? The heavy metals may have got there by slow accumulation. Sample of drill cuttings of shale while drilling an oil well in Louisiana , United States. Succession of shale overlying thick bed of fossiliferous chert, Pottsville Formation, Pennsylvanian, Ohio.

Shale facts for kids Kids Encyclopedia Facts. All content from Kiddle encyclopedia articles including the article images and facts can be freely used under Attribution-ShareAlike license, unless stated otherwise.

Just one or two percent organic materials can impart a dark gray or black color to the rock. In addition, this black color almost always implies that the shale formed from sediment deposited in an oxygen-deficient environment. Any oxygen that entered the environment quickly reacted with the decaying organic debris. If a large amount of oxygen was present, the organic debris would all have decayed.

An oxygen-poor environment also provides the proper conditions for the formation of sulfide minerals such as pyrite , another important mineral found in most black shales. The presence of organic debris in black shales makes them the candidates for oil and gas generation. If the organic material is preserved and properly heated after burial, oil and natural gas might be produced. The Barnett Shale, Marcellus Shale , Haynesville Shale , Fayetteville Shale , and other gas-producing rocks are all dark gray or black shales that yield natural gas.

Gray shales sometimes contain a small amount of organic matter. However, gray shales can also be rocks that contain calcareous materials or simply clay minerals that result in a gray color. Utica and Marcellus Shale: Two black organic shales in the Appalachian Basin are thought to contain enough natural gas to supply the United States for several years.

These are the Marcellus Shale and Utica Shale. Shales that are deposited in oxygen-rich environments often contain tiny particles of iron oxide or iron hydroxide minerals such as hematite , goethite, or limonite.

Just a few percent of these minerals distributed through the rock can produce the red, brown, or yellow colors exhibited by many types of shale. The presence of hematite can produce a red shale. The presence of limonite or goethite can produce a yellow or brown shale. Green shales are occasionally found. This should not be surprising because some of the clay minerals and micas that make up much of the volume of these rocks are typically a greenish color.

Natural gas shale well: In less than ten years, shale has skyrocketed to prominence in the energy sector. New drilling and well development methods such as hydraulic fracturing and horizontal drilling can tap the oil and natural gas trapped within the tight matrix of organic shales. Hydraulic properties are characteristics of a rock such as permeability and porosity that reflect its ability to hold and transmit fluids such as water, oil, or natural gas. Shale has a very small particle size, so the interstitial spaces are very small.

In fact they are so small that oil, natural gas, and water have difficulty moving through the rock. Shale can therefore serve as a cap rock for oil and natural gas traps, and it also is an aquiclude that blocks or limits the flow of groundwater. Although the interstitial spaces in a shale are very small, they can take up a significant volume of the rock. This allows the shale to hold significant amounts of water, gas, or oil but not be able to effectively transmit them because of the low permeability.

The oil and gas industry overcomes these limitations of shale by using horizontal drilling and hydraulic fracturing to create artificial porosity and permeability within the rock. Some of the clay minerals that occur in shale have the ability to absorb or adsorb large amounts of water, natural gas, ions, or other substances.

This property of shale can enable it to selectively and tenaciously hold or freely release fluids or ions. Expansive soils map: The United States Geological Survey has prepared a generalized expansive soils map for the lower 48 states. Shales and the soils derived from them are some of the most troublesome materials to build upon.

They are subject to changes in volume and competence that generally make them unreliable construction substrates. The clay minerals in some shale-derived soils have the ability to absorb and release large amounts of water. This change in moisture content is usually accompanied by a change in volume which can be as much as several percent. These materials are called " expansive soils. Buildings, roads, utility lines, or other structures placed upon or within these materials can be weakened or damaged by the forces and motion of volume change.

Expansive soils are one of the most common causes of foundation damage to buildings in the United States.