Lab 7 notes

# Lab 7 notes - Lab 7 Geologic Structures Maps and Block...

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Lab 7. Geologic Structures, Maps, and Block Diagrams 1. Structural Geology : the study of how geologic units are arranged when they are first formed and how they are deformed afterward. Deformation : changes that take place in the original location: orientation, shape and volume of rock body Stress and Strain : when rocks are subjected to severe stress (directed pressure), they may eventually undergo strain (deformation). Stress induces strain in rocks. 2. Geological Maps, Cross Sections and Block Diagrams : Geological map : shows the distribution of rock bodies at the Earth’s surface. The rocks are divided into rock units based on color, texture, or composition. Such rock units are called formation . Formations can be further divided into members and beds. Contacts are the boundaries between geological units, which form lines on the geological map. A geologic map also shows the topography of the land surface, so it’s also a topographic map. Cross Section : displays vertical slice through Earth, use to reveal the orientation and arrangement of rocks Block Diagram : a combination of geologic map and cross section, performs as a 3D model of a portion of the Earth’s crust. 3. Attitude : orientation of a rock unit or surface. Geologists use two lines to describe the attitude: strike and dip. Strike : a line formed by the intersection of a horizontal plane and an inclined layer. Strike can be expressed as a quadrant bearing (e.g. N45ºW) or azimuth bearing (e.g. 315º, North =0º, East = 90º, South=180º, West=270º ) Dip : it has both direction and angle. Dip direction: the plunge of line of the greatest slope on an inclined plane, which is always perpendicular to strike. Dip angle: the angle between a horizontal plane and the inclined layer. 4.

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Lab 7 notes - Lab 7 Geologic Structures Maps and Block...

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