Physical Geography

Internal Forces of Change

Continental Drift Plate Tectonics The theory that the land of the earth was once connected as one large super continent (Pangaea) and has moved “drifted” to its current locations (still moving) Plate Tectonics The theory that the crust of the earth is broken up into plates (8 major and many minor) that “float” on the mantle

The plate boundaries of the world.

Subduction When a sea plate and continental plate collide, the heavier sea plate DIVES under the lighter continental plate. The sea plate then is heated and becomes magma which escapes through volcanoes.

Spreading When sea plates pull apart leaving a rift, or deep crack. Magma wells up between the two plates to make underwater volcanoes and ridges.

Volcano mountain formed by lava (magma) that breaks through the earth’s crust.

Ring of Fire area along the edge of the Pacific Ocean that is a zone of frequent earthquakes and volcanoes.

Folding when moving plates squeeze the earth’s surface until it bends the layers of rock.

Faulting When moving plates grind past each other, creating cracks in the crust.

Earthquake sudden, violent moving of plates along a fault where built up pressure suddenly snaps and shifts.

Water erosion fast-moving water cuts into the land as it flows downstream. Ocean waves can also erode coastal cliffs. WATER is the most significant cause of erosion. Water Erosion creates canyons

Delta the flat, low-lying plain that sometimes forms at the mouth of a river from deposits of sediments. Deltas form as rivers empty their water and sediment into another body of water, such as an ocean, lake, or another river. They are called deltas because the alluvial deposit at the river’s mouth looks like the Greek letter delta (∆)

EARTH: The Apple of Our Eye