1. WEATHERING AND EROSION
EPIC
WEATHERING AND EROSION
REVIEW FOR 6TH GRADE
LET'S GOOOOO

2. What even is a rock?
Elements + chemical compounds → hard, solid materials of Earth's surface
Minerals
Elements and compounds found in rocks
All minerals are solid

3. Weathering chemical or mechanical
breaking down of rocks by exposure to air, moisture, organic materials
small-scale, local changes on rocks

4. Mechanical/Physical Weathering
breaks rocks into smaller pieces without changing them chemically
frost wedging, plants, animals, gravity

5. Frost Wedging Water seeps into cracks in rock and freezes
When water freezes, it expands and breaks the rock

6. Living Organisms Growing roots put pressure on rock
Burrowing loosens and weakens rock

7. Gravity Exposes new surfaces for physical and chemical weathering
Avalanches, rock slides

8. Chemical Weathering
decomposition of rock due to chemical reactions between rock and chemicals in the environment
changes chemical composition of rock
materials acted upon

9. Chemical Weathering, cont'd
natural acids and oxygen
water + carbon dioxide = carbonic acid
acid rain – caused by pollution
sulfur released into air by factories, combines with water

10. Erosion
rock and soil materials are loosened and transported from one place to another
KEY = MOVEMENT
large-scale changes over great distances
From canyons and valleys all the way to
deltas and sand dunes

11. Wind sand grains carried by strong winds act like sandpaper
scrape away little pieces of rock and soil from hills and mountains
can pick up soil from plants or fields and transport to other areas

12. Water Runoff: water that flows over Earth's surface
Carries sediment, soil → eroding land

13. Water, cont’d Three factors influence amount of water erosion:
Rainfall intensity and runoff – more rain, more erosion
Steepness of slope – steeper slope, more erosion
Vegetation/obstacles – more rocks and plants, less erosion

14. Soil mixture of weathered rock, organic matter, and water
sand, gravel, humus
end result of weathering and erosion
humus - organic component of soil
comes from decomposing plant and animal
material

15. Structure of Earth Crust: surface of Earth
Mantle: semi-solid middle layer
Convection currents in mantle cause movement of tectonic plates
Core: middle of Earth, iron and nickel
Extreme heat and under extreme pressure

16. Convection Currents
Convection currents: hot material rises and cool material sinks
CC in the mantle force materials up onto the Earth’s crust
Creates new crust, pushing tectonic plates into one another
This causes continental drift!

17. Rock Types Igneous rock: formed by the cooling of lava or magma
Sedimentary rock: rock formed when sand, mud, and pebbles are deposited on top of each other
Layers squashed into each other until they form rock
Metamorphic rock: changed
by extreme heat and pressure

18. Steps 1-3 of the Rock Cycle
Molten rock from the mantle rises to the surface and creates new crust
- This molten rock cools and forms igneous rock
As a result of weathering, rock breaks down
Over time, broken down rocks are layered on top of each other to form sedimentary rock

19. Steps 4-7 of the Rock Cycle
As more and more rock builds up, pressure and temperature
increase a lot
This increased pressure and temperature form metamorphic rock
Metamorphic rock sinks into the mantle and melts into
magma, becoming part of the mantle
Through convection, the magma is pushed back up to
the surface and creates new igneous rock
AND THE CYCLE REPEATS

20. Rock Cycle Diagram