Download Science 7 – Unit #5

Science 7 – Unit #5 - Topic 3 – Erosion
Name: _________________
1. Erosion is the
movement of rock and mineral grains from one place to another.
Sediments come from larger rocks that worn down.
2. Weathering is when minerals or other materials are broken down or worn out by the
weather. Ex) concrete can wear down when it is rained on heavily
There are 3 Types of Weathering. Please read p. 373-374 for key pts. and examples below.
1. Mechanical Weathering
- the physical break-up of rocks weathered down
Example: sand blasting, gravity, frost wedging
Mechanical Weathering is the part of the process responsible for wearing away. Sedimentation
is the part of the process responsible for building up.
2. Chemical Weathering
- the break down of minerals and rocks through chemical reactions
Example: acid rain contains dissolved chemicals from air pollution
3. Biological Weathering
- when living organisms break down rocks/minerals (both mechanically and chemically)
Example: when tree roots force its way into rock cracking and breaking it apart
3. 4 Key Agents of Erosion – p. 376
Glaciers, Gravity, Wind , and Water are the four key agents of Erosion.
1. Glaciers – a huge mass of ice the travels slowly over land; leaves striations (scratches in
the rock)
2. Gravity – is one of the forces responsible for landslides and rock slides (Frank Slide)
3. Wind – picks up loose sediments which scrape against rocks (similar to sand blasting)
4. Water – collects sediments or moves them to a new place (ex: rivers running quickly,
Calgary Flood)
Define Abrasion: rubbing sediments to gradually wear away
4. What is a Striation? P.376
The scratches or marks left behind from a glacier passing over
5. What is a Moraine? P.376-377
Eroded sediments get pushed in front of a glacier and piled up along its sides.
6. What is Erratic? P.377
When glaciers begin to melt and retreat, the melt water forms channels and deposits sediments
in new locations. The large rocks left behind are called erratics.
7. Gravity is one force that is responsible for landslides and rockslides. What can be done to
prevent slides from happening? Describe Frank Slide p. 377
- retaining walls can be built to help keep the land/rocks from sliding
- Frank Slide: the most disasterous rock slide in Canadian history. A town was covered in rocks
killing 70 people.
8. How does a V-shaped valley form?
Rivers can cut straight into rock forming canyons or steep valleys. Ex: Grand Canyon
* Topic 3 Review p. 380 - # 1-4