Forces of Change

Rose Wright, Elizabeth Robinson, Cody Stoelzle, Don Harris

Forces of Change

core—the very center of Earth; two parts: inner core, which is made of solid metals due to the pressure on it, and the outer core made of liquid metal.

mantel—a thick layer of hot, dense rock which is partially melted.

crust—a rocky shell forming the earth’s surface

A Layered Planet

continental drift: theory that the continents were once joined and then drifted apart. Thus it is also believed that the plates float freely upon the mantel.

plate tectonics: all of the physical processes that create Earth’s physical features.

magma: molten rock from the mantel.

Plate Movement

Internal Forces

subduction—process by which two plates collide and the lighter of the two sinks beneath the other. This process can also cause mountains, because the lighter one pushes the other upwards.

accretion—the pieces of Earth’s crust come together slowly as the sea plates slide under continental plates. This is the opposite of spreading, which causes trenches.

Colliding & Spreading Plates

Himalayas: a mountain range south of Asia being the tallest in the world

folds—bends in the layers of rock, similar to subduction but involving layers of the same mass.

faults—cracks in the earth’s crustfaulting—when land is folded and reaches a

breaking point. The land then shatters and the shards then grind against each other creating small earthquakes.

Folds & Faults

San Andreas Faultline; one of the most famous fault lines in the world, caused by faulting. The scar you see here is from the last time a faulting happened in this area.

Kobe—place in Japan where disasterous earthquakes have happened.

San Francisco—city in California; site of many earthquakes. Most famous being a massive fault shift that tore the city apart.

Ring of Fire—one of the most earthquake- and volcanic-prone areas on the globe.

Earthquakes—caused by faulting

One of the biggest and fastest-acting forces to change Earth’s features.

Volcanic Eruptions

External Forces of Change

Weathering: a force that breaks down rocksErosion: wears away Earth’s surface by wind, glaciers, and moving water

Movement of dust, sand and soil. It’s a constant force of change responsible for some of the most obscure geographical features.

Wind Erosion

moraines—rock and debris left over when glaciers melt.

Greenland—a northern, Scandinavian country almost completely covered in ice.

Antarctica—continent much like Greenland, covered in glacial sheets that are increasingly receding.

Glacial Erosion

glaciers—large bodies of ice that move across Earth’s surface

Water erosion begins when

spring- and rain-water flow down in streams that cut through land.

This force is responsible for the Grand Canyon

Water Erosions Grand Canyon: product of water erosion