Constructive and

Destructive Forces Processes That Act Upon Earth’s

Surface Features

What are Constructive and

Destructive Forces?

• Constructive Force

– A constructive force is

a process that raises

or builds up the

surface features of the

Earth.

• Destructive Force

– A destructive force is a

process that lowers or

tears down the surface

features of the Earth.

What Are Surface Features?

– Surface features are landforms and bodies of

water that cover the Earth’s surface such as:

• mountains

• valleys

• canyons

• gorges

• beaches

• sand dunes

• barrier Islands

• flood-plains

• moraines and drumlins

• volcanoes

• oceans

• lakes

• rivers

How Can a Surface Feature be

Changed by a Constructive Force?

– Natural forces such as wind, water, ice,

through the process of deposition.

• Deposition is the process of dumping sediment,

dirt, rocks, or particles in one place.

– The movement of the Earth’s crust through

Plate Tectonics

Constructive Force Examples of Deposition

Constructive

Process

Surface

Feature

Force/Agent

Deposition

Deltas water / river

Floodplains water / river

Beaches and

Barrier Islands

water / ocean

long-shore

current

Sand dunes wind

Moraines and

drumlins

Ice / glacier

Other Constructive Forces

Constructive

Process

Surface

Feature

Force

Folding Mountains Plate

tectonics

Faulting Mountains Plate

tectonics

Earthquake Trench

Fault

Plate

tectonics

Volcanic

Activity

Mountains

Islands

Plate

tectonics

How Can a Surface Feature be

Changed by a Destructive

Force?

– Physical or Chemical Weathering

• Weathering is the breaking down of rock into

sediment.

– Natural forces such as wind, water, ice,

through the process of erosion.

• Erosion is the movement of sediment from one

place to another.

Changing the Earth’s Surface by a

Destructive Force Examples of Weathering

• Mechanical / Physical

Weathering

– Temperature Change-Freezing and thawing of Rock

– Ice Wedging-Water freezing and expanding in cracks of rock

– Impact of organisms

• Root Pry

• Animals burrowing

• Chemical Weathering

– Oxidation / rusting

– Carbonic Acid / acid rain

• Caverns

– Impact of organisms

• Secretion of acid from Lichen

Destructive Force Examples of Erosion

Destructive

Process

Surface

Feature

Force/Agent

Erosion

Canyons,

Gorges, V-

Shaped Valleys

Water

Sea Arches,

Sea Stacks

Water

Buttes, Desert Wind

U-Shaped Valleys Ice

Mudslide,

Sinkholes

Gravity

Other Destructive Forces

• Volcanic Activity

– Movement of Earths Crust (Plate tectonics)

• Reshaping of Mountains

• Earthquakes

– Movement of Earths Crust (Plate tectonics)

• Trenches

– cracks in the Earth Curst

What Do You Think?

Deposition is a process

that…

A. Dissolves sediment

B. Breaks down rock to form sediment

C. Removes sediment from landforms

D. Drops sediment to form landforms

Where do deltas form?

A. In desert areas

B. At river mouths

C. On the banks of rivers

D. In valleys formed by glaciers

Long shore currents

help create…

A. Beaches

B. Dunes

C. Rivers

D. Drumlins

Volcanoes can create

new land when they

release…

A. Lava

B. Water

C. Faults

D. Mud

What forms moraines

and drumlins?

A. Wind

B. Rivers

C. Glaciers

D. Volcanoes

What landform forms

from deposition at the

mouths of rivers?

A. a delta

B. a floodplain

C. a sand dune

D. a moraine

What is weathering?

A. A type of climate

B. The transport of sediment

C. The breakdown of rock

D. The aging of rock

Which of these is

caused by chemical

weathering?

A. desert pavement

B. formation of U-shaped valleys

C. formation of rust

D. ice expanding in cracks in rock at is

weathering?

How do earthquakes

change the land?

A. They transport sediment.

B. They form cracks in the surface.

C. They release ash and lava.

D. They cause chemical weathering.

A river can form …

A. Sea arches.

B. U-shaped valleys.

C. V-shaped valleys.

D. Desert pavement.

Deposition forms these

features on coasts.

A. drumlins

B. floodplains

C. barrier islands

D. U-shaped valleys

What causes V-shaped

valleys to form?

A. deposition at river mouths

B. erosion by rivers

C. weathering by wind

D. erosion by glaciers

What does erosion do?

A. breaks down rock physically

B. moves broken pieces of rock

C. changes rock chemically

D. change sediment into rock