Many geologists classify a landform as a mountain if it is at least 300 meters or more above its surrounding topography. Mountains have steep sloping sides, rounded or sharp ridges, and a peak or summit. Hills are not as... More »

Rocks are important because geologists use evidence from them to learn about what the Earth was like in the past. They allow scientists to build a historical record of the planet to learn what events occurred before peop... More »

Some famous geologists in history include Eratosthenes, James Hutton, Sir Charles Lyell, Mary Anning and Alfred Wegener. Others include Gene Shoemaker, William Smith, Friedrich Mohs and Inge Lehmann. More »

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The principle of original horizontality refers to an assumption by geologists that all layers of sedimentary rock were horizontal when they were formed. This is one of the basic principles of stratigraphic succession, wh... More »

As of 2014, geologists contend that granite is a plutonic rock resulting from deeply buried shale and sandstone that melted, partially melted or metamorphosed, depending on the category of granite in question. Igneous gr... More »

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The fossil record refers to the collection of physical and research evidence that paleontologists and geologists have used to prove the veracity of evolutionary theory. The physical evidence in the fossil record comes fr... More »

Stratigraphic columns are illustrations made by geologists to represent the relative composition, thickness and scope of layers of rock, such as in a canyon, a volcano or a cliff. Some drawings are black and white with l... More »