1. Focus: Weathering and Erosion/Begin Evolution
Earth History: Day 26
Focus: Weathering and Erosion/Begin Evolution
12/14/17
Science starter: Copy and answer.
A rock formation in a land area contains fossils. Over time, tremendous heat and pressure change the formation to produce a harder rock formation without fossils. Which change in rock type has occurred in this land area?
*Igneous rock has turned into sedimentary rock
*Igneous rock has turned into metamorphic rock
*Sedimentary rock has turned into igneous rock
*Sedimentary rock has turned into metamorphic rock.

2. Plan for the Day
Review key concepts related to weathering and erosion.
Begin Evolution unit.

3. Homework
Quiz Monday over soil, weathering, and erosion. Study those webquests.
Workbook pages – due Monday
*Be prepared for another web quest next. Yep.

4. What are the causes and effects of weathering and erosion?
E.Q.
What are the causes and effects of weathering and erosion?

5. Let’s go over key concepts about “Weathering and Erosion”
Let’s go over key concepts about “Weathering and Erosion”. Take out your web quest.

6. Weathering and Erosion – Key Ideas
Weathering is the wearing away of the surface of rock, soil, and minerals into smaller pieces.
Weathering can occur due to chemical and mechanical processes.
Example of weathering: Wind and water cause small pieces of rock to break off the side of a mountain.
Erosion is the movement of particles away from their source.
Example of erosion: Wind carries small particles of rock away from the side of a mountain.

7. Weathering – Chemical and Mechanical Processes
*Chemical Weathering – decomposition of rock and soil due to chemical reactions
-Ex: acid rain wears away statues and buildings; oxidation causes metals to rust
*Mechanical Weathering – decomposition of rock and soil due to mechanical forces – pushes and pulls, impacts
-Ex: wind, water, ice/frost, gravity, compression and contraction of materials due to heat

8. Climate and Weathering
The two key climate factors that affect the rate of weathering are temperature and moisture.
Temperature -The rate of most chemical reactions increases as the temperature increases (you learned this in chemistry), so rocks in warm climates experience faster rates of chemical weathering than rocks in cool climates. Cold climates increase rates of physical (mechanical) weathering, because different minerals expand and contract at different rates when they are heated, so repeatedly heating and cooling the rock (as the day warms up and cools down) eventually causes it to fracture. Think about how potholes get worse in the winter.

9. Temperature and Weathering

10. Climate and Weathering
The two key climate factors that affect the rate of weathering are temperature and moisture.
Deserts (get cold at night) and mountain climates experience a wide range of temperatures so physical (mechanical) weathering through fracturing accelerates in these environments.

11. Climate and Weathering
Moisture and rainfall are the other critical factor.
Moist climates accelerate the rates of chemical weathering, so if a rock is prone to chemical weathering it will break down more rapidly in a wet climate. In general, warm moist climates accelerate chemical weathering while cold, dry climates (think about the dunes in a desert) accelerate physical (mechanical) weathering. Dry ground cannot absorb water as quickly, therefore, you have increased runoff which increases erosion. The rate of weathering also depends on the type of rock, as well as biological factors, like tree roots, that break up rocks.

12. Climate and Weathering - Review
Turn and talk.
What type of climate is more conducive to mechanical weathering and why?
Cold, dry climates increase rates of physical (mechanical) weathering, because different minerals expand and contract at different rates when they are heated, so repeatedly heating and cooling the rock eventually causes it to fracture.

13. Climate and Weathering - Review
Turn and talk.
What type of climate is more conducive to chemical weathering and why?
Warm, moist climates accelerate chemical weathering because the rate of most chemical reactions increases as the temperature increases

14. Effects of Weathering and Erosion
Changes in the slopes and texture of rock structures, hills, and valleys
Landslides
Sinkholes and caves
Wearing away of buildings, statues, and roads
Soil, pollutants, and other harmful substances from roads and farms washing into waterways
Reduction in the area of a beach or shoreline
Creation of river deltas and alluvial fans

15. Alluvial Fans and Deltas

16. Alluvial fans are sedimentary landforms deposited by flowing water
Alluvial fans are sedimentary landforms deposited by flowing water. From above you can easily see their fan, or pie wedge shape. Alluvial fans are often found at the base of arid/ semi-arid mountain ranges where intermittent streams flow. For a stream to be intermittent it flows only went it rains or snow melts. Sediment drops out of stream flow as energy decreases due to widening of the channel. Over time sediment builds up in the channels at the base of mountains and forces the stream to carve another channel. When channels fill in the process starts again. Streams filling in and moving to the side form fan shaped deposits.

17. Deltas
When a river reaches a lake or the sea (we call this the “mouth” of a river), the water slows down and loses the power to carry sediment. The sediment is dropped at the mouth of the river. Some rivers drop so much sediment that waves and tides can't carry it all away. It builds up in layers forming a delta. Deltas have a fairly flat section called a delta plain that is above water. The river cuts many small channels through the delta plain. These channels are called distributaries. New sections of delta build up at the mouths of the distributaries.

18. The planet's longest river, the Nile, has a mouth that forms a famous triangle called the Nile Delta. Most of Egypt's habitable land is within the Nile Delta and along the Nile River. With a rich and diverse cultural history, the Nile Delta is one of northern Africa's most fertile regions -- people have farmed it for thousands of years.
Nile Delta Quick Facts
The word delta gets its name from the fact that the Greek letter delta looks like the triangular area at the mouth of the Nile. Deltas become complex over time as sediments build up in different areas. A river may even alter its course when sand barriers, channels and marshes form in its delta. With an area of around 22,000 square kilometers (8,494 square miles), the Nile Delta is Egypt's main oil and gas producing region.

19. Nile River Delta

20. Nile River Delta

21. The Mississippi River Delta region is a 3-million-acre (12,000 km2) area of land that stretches from Vermilion Bay on the west, to the Chandeleur Islands in the Gulf of Mexico on the southeastern coast of Louisiana.[1] It is part of the Louisiana coastal plain, one of the largest areas of coastal wetlands in the United States.
The modern Mississippi River Delta formed over the last approximately 7,000 years as the Mississippi River deposited sand, clay and silt along its banks. The Mississippi River Delta is a river-dominated delta system, influenced by the largest river in North America.

22. Mississippi River Delta

23. Mississippi River Delta

24. Start evolution day 1
..\Unit 4 Evolution EE\Unit 4 Evolution Day pptx

25. Wrap-up: