Two Types of ForcesDestructive Forces: processes that destroy

landforms.2 types: Slow (weathering) and Fast (Erosion)Ex. landslides, volcanic eruptions, earthquakes,

floods

Constructive forces: forces that build up an existing landform or create a new one. Caused by: water, gravity, wind and glaciers.Ex: deposition, landslides, volcanic eruptions, floods

WeatheringWeathering is the breaking down of rocks

into smaller pieces. Rain, ice, and atmospheric gases cause this.

Physical/ Mechanical weatheringRocks are broken into smaller pieces by

physical agents. Ice wedging. Plant and animal actions. Water

Chemical weatheringBreaking down of rocks due to the chemical

change in their composition. Air and water often cause this. Oxidation (rust) and acid rain.

ErosionThe process that moves rock material at

Earth’s surface and caries it away. Movement of the rock particles.

Causes of erosion…Gravity-landslides/rockslides.Running water-rivers form canyonsGroundwater-underground water forms

caves/cavernsGlaciers-rocks are carried under a glacier. Wind-rock particles are blownOcean currents-sand is moved along a beach

by waves.

Constructive Landform ProcessesProcesses that build up Earth’s surface and

cause the land surface to rise.

DepositionThe process by which eroded material is

dropped off or deposited in a new area. Gravity WaterWindGlaciers Ocean currents

Volcanic EruptionsVolcano: ??? an opening in the

Earth’s crust through which steam, lava and ashes erupt.

Cause both destructive and constructive changes to landforms.

Volcanoes can be constructive, but also destructive…

Folding and FaultingForces in Earth’s surface caused by the

movement of Earth’s plates squeezes and bends the surface of Earth.

Folding occurs when the crust is bent upward or downward.

Faulting occurs when the crust is actually broken.

Volcanic ActivityThe movement of liquid rock underground

and on earth’s surface. Magma is hot liquid rock beneath the Earth’s

surface. Magma is less dense than solid rock so it rises

to the surface. This forms a volcano.

When volcano’s erupt, they release hot liquid rock called lava.

Lava will harden forming new landforms.

Mount St. Helens

Saint Helen’s Before

Saint Helen’s After

EarthquakesEarthquakes: the

shaking of Earth’s surface caused by the release of energy along a fault.

San Andreas Fault, California

Volcanoes & EarthquakesTectonic Plates, Volcanoes & Earthquakes

Landforms from ErosionCanyons/valleys

Flowing water removes sediment.

Sea cliffsWaves erode rock making steep cliffs.

Sea caves, arches, and stacks.

Landforms from DepositionFlood plains

Sediments deposited when rivers overflow their banks.

Deltas and Alluvial FansWhen a stream flows into a large body of water

(lake/ocean) or onto land, it deposits sediment in a fan shape.

Delta-fan shaped pattern in a lake or ocean.Alluvial fan-fan shaped pattern on land.

Water Erosion & DepositionRiver Delta-

Deposits of sediment at the mouth of the Mississippi River creating new land called a delta.

BeachesArea of shoreline made up of sediment

deposited by ocean currents and waves.

Landforms from Folding and FaultingBlock mountains

Large areas of Earth are forced upwards in a fault.

Rift valleyWhen two pieces of Earth’s surface are

separating from each other.

Folded mountainsWhen the surface of Earth is bent upward

making a mountain.

Landforms from Volcanic ActivityVolcanoes

Dome mountainMagma forces the surface of Earth up into a

dome shaped mountain.

Plateau

PrimetimeWhat are two examples of destructive forces?What are four examples of constructive

forces?Give an example where constructive and

destructive forces work together to create a landform.