Dike (geology)

A dike or dyke, in geological usage, is a sheet of rock that formed in a fracture in a pre-existing rock body. Dikes can be either magmatic or sedimentary in origin. Magmatic dikes form when magma intrudes into a crack then crystallizes as a sheet intrusion, either cutting across layers of rock or through an unlayered mass of rock. Clastic dikes are formed when sediment fills a pre-existing crack.

Magmatic dikes

An intrusive dike is an igneous body with a very high aspect ratio, which means that its thickness is usually much smaller than the other two dimensions. Thickness can vary from sub-centimeter scale to many meters, and the lateral dimensions can extend over many kilometres. A dike is an intrusion into an opening cross-cutting fissure, shouldering aside other pre-existing layers or bodies of rock; this implies that a dike is always younger than the rocks that contain it. Dikes are usually high-angle to near-vertical in orientation, but subsequent tectonic deformation may rotate the sequence of strata through which the dike propagates so that the dike becomes horizontal. Near-horizontal, or conformable intrusions, along bedding planes between strata are called intrusive sills.

Geology

Geology (from the Greek γῆ, gē, i.e. "earth" and -λoγία, -logia, i.e. "study of, discourse") is an earth science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which they change. Geology can also refer generally to the study of the solid features of any celestial body (such as the geology of the Moon or Mars).

Geology gives insight into the history of the Earth by providing the primary evidence for plate tectonics, the evolutionary history of life, and past climates. Geology is important for mineral and hydrocarbon exploration and exploitation, evaluating water resources, understanding of natural hazards, the remediation of environmental problems, and for providing insights into past climate change. Geology also plays a role in geotechnical engineering and is a major academic discipline.

Geologic materials

The majority of geological data comes from research on solid Earth materials. These typically fall into one of two categories: rock and unconsolidated material.

The Palm Beach Post

The Palm Beach Post is a major American daily newspaper serving Palm Beach County in South Florida, and the Treasure Coast area. It is the 80th largest daily newspaper in the United States and the 7th largest in Florida.

History

The Palm Beach Post began as The Palm Beach County, a weekly newspaper established in 1908. In January 1916, the weekly became a daily, morning publication known as The Palm Beach Post.

In 1934, Palm Beach businessman Edward R. Bradley bought The Palm Beach Post and The Palm Beach Times, the afternoon daily (except on Sunday). In 1947, both were purchased by longtime resident John Holliday Perry, Sr., who owned a Florida newspaper chain of six dailies and 15 weeklies. In 1948, Perry purchased both the Palm Beach Daily News and the society magazine Palm Beach Life.

In June 1969, Cox Enterprises, based in Atlanta, purchased Perry's Palm Beach and West Palm Beach publications and formed Palm Beach Newspapers, Inc. Cox was founded by James M. Cox, a former Ohio governor and the 1920 Democratic presidential candidate who built a media company that today includes daily newspapers; weekly newspapers, radio and television stations; U.S. cable TV systems, local Internet media sites and Mannheim auto auction locations.

Palm Beach

Palm Beach may refer to:

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Lake Okeechobee

Lake Okeechobee (US /oʊkiˈtʃoʊbi/), locally referred to as "The Lake", "Florida's Inland Sea", or "The Big O", is the largest freshwater lake in the state of Florida. It is the seventh largest freshwater lake in the United States and the second largest freshwater lake (the largest being Lake Michigan) contained entirely within the contiguous 48 states. However, it is the largest freshwater lake completely within a single one of the lower 48 states. Okeechobee covers 730 square miles (1,900 km²), approximately half the size of the state of Rhode Island, and is exceptionally shallow for a lake of its size, with an average depth of only 9 feet (2.7 metres). The lake is divided between Glades, Okeechobee, Martin, Palm Beach, and Hendry counties. All five counties meet at one point near the center of the lake.

History

Lake Okeechobee sits in a shallow geological trough that also underlies the Kissimmee River Valley and the Everglades. The trough is underlain by clay deposits that compacted more than the limestone and sand deposits did along both coasts of peninsular Florida. Until about 6,000 years ago, the trough was dry land. As the sea level rose, the water table in Florida also rose and rainfall increased. From 6,000 to 4,000 years ago, wetlands formed building up peat deposits. Eventually the water flow into the area created a lake, drowning the wetlands. Along what is now the southern edge of the lake, the wetlands built up the layers of peat rapidly enough (reaching 4-to-4.3-metre (13 to 14 ft) thick) to form a dam, until the lake overflowed into the Everglades. At its capacity, the lake holds 1 trillion gallons of water and is the headwaters of the Everglades.