Unit 7: Forces that Change the Earth Overview

Tectonic Plates	Large pieces of Earth’s outer layer that fit together like pieces of a puzzle
Lithosphere	The top layer of the Earth which consist of the crust and upper mantle
Asthenosphere	A zone in Earth’s mantle where heat and pressure cause rock to be soft and fluid. Tectonic plates move on top of this zone
Plate Boundary	A place where tectonic plates meet (either convergent, divergent or transform)
Fault	A fracture in Earth’s crust
Sea Floor Spreading	The process by which new oceanic crust is formed at a divergent boundary
Mid-Ocean Ridge	A mountain range on the ocean floor caused by volcanic activity at a divergent boundary
Rift Valley	A low lying area resulting from a divergent boundary on land
Subduction Zone	A place where one tectonic plate sinks underneath another at a convergent boundary
Trench	Long steep valleys in the ocean floor caused by one plate sinking under another at a subduction zone
Topography	The shape and size of land features on Earth’s surface
Topographic Map	A map that uses contour lines to show the elevation of land features
Contour Line	A curved line on a map that connects the points of equal elevation
Contour Interval	The change in elevation between two contour lines on a map
Index Contour	A thick contour line which has an elevation label
Alluvial Fan	An area where streams flow onto flatter land, slow down, and deposit sediment
Delta	An area at the mouth of a river where deposited sediment flatten the land
Floodplain	A flat area around rivers where sediment has been deposited from cycles of flooding
Barrier Islands	A long narrow island shaped by deposition which forms parallel to the shoreline