Warm Up Wednesday, March Define mechanical weathering. Define chemical weathering. 2. What do you think causes weathering to happen faster?

Rates of Weathering What is differential weathering? How does surface area affect the rate of weathering? How does climate affect the rate of weathering? Why do mountaintops weather faster than rocks at sea level?

What Factors Affect the Rate of Weathering? 1. make up of rock (composition) 2. surface area 3. climate 4. elevation

What can effect the rate of weathering? #1 Make-up (composition) of Rock

Differential Weathering Softer rocks weather more quickly than harder rocks. Differential weathering is a process by which softer, less weather-resistant rocks wear away and leave harder, more weather-resistant rocks behind.

Example of Differential Weathering: Devils Tower Devils Tower appears as it does today because of differential weathering. As surrounding rock was worn away, the hard rock of the tower was exposed.

What can effect the rate of weathering? #2 Surface Area

#2 Surface Area Weathering takes place on the outer surface of rocks.

#2 Surface Area If a large rock is broken into smaller pieces, weathering of the rock happens much faster. Explain: – This is because the broken pieces expose more of the rock to weathering. –Multiple pieces of one rock will have a greater amount of surface area for the same amount of volume.

Surface area. If these all contain the same volume of rock, which one will weather faster?

Total Surface Area to Volume

What can effect the rate of weathering? #3 Climate

#3 Climate Climate: overall temperature and weather of a region over a long period of time.

#3 Climate- 2 ways climate speeds up weathering. 1.Chemical weathering: Will happen faster in warm, humid (moist) climates than in cold, dry climates.

#3 Climate- 2 ways climate causes weathering. How does climate speed up chemical weathering? Explain: Warmth and moisture will speed up the process of oxidation (rusting), thus weathering happens faster.

Climate- 2 ways climate speeds up weathering 2. Mechanical weathering- Ice and temperatures changes.

Climate- 2 ways climate speeds up weathering Explain: When water gets into the crack of rock and freezes, it expands, pushing the rock apart. Warmer temperatures thaw (melt) ice. Freezing temperatures freeze the water, expand, and push the rock apart further Freeze-thaw(melt)-freeze-thaw(melt): pattern that causes ice wedging.

What can effect the rate of weathering? #4 Elevation

#4 Elevation- Exposure Higher elevation= more weathering. Low elevation= less weathering.

#4 Elevation Explain: Higher elevations (mountain tops) are exposed to more wind, rain, and ice than rocks at sea level or lower elevations. The increase of these agents causes more mechanical and chemical weathering. Question: Why will mountain tops weather away faster than rocks at a lower elevation?

#4 Elevation- Gravity Gravity Gravity affects the rate of weathering: –1. Steepness of mountain slope: when it rains, water runs off steep mountain slopes more quickly, carrying sediment away. –2. When sediment is carried away, it exposes new to rock to weathering. –3. Abrasion As rocks tumble down mountain side, they hit each other, breaking them apart more and increasing the surface area of rock that will be exposed to more weathering.

Weathering and Elevation The Ice, Rain, and Wind that these mountain peaks are exposed to cause them the weather at a fast rate.

Let’s Sum it Up Now….Let’s see what you learned! Get out notebook paper, number the paper 1-11.

Let’s Sum it Up 1. _________rocks weather more slowly than softer rocks. (hard; soft) 2. The more surface area of a rock that is exposed to weathering, the ________ the rock will be worn down. (faster; slower) 3. Chemical weathering occurs _________ in warm, humid climates. (faster; slower) 4. Weathering occurs faster at ______ elevations because of an increase in ice, rain, and wind. (high; low)

Quick Check 5. What four factors determine the rate at which rock weathers?

Quick Check 6. The process by which softer, less weather resistant rocks wear away and leave harder, more weather-resistant rocks behind is called A. mechanical weathering B. chemical weathering C. differential weathering D. acid precipitation

Quick Check 7. Weathering takes place A. on the outer surface of rocks. B. on all rocks equally. C. inside the rocks.

Quick Check 8. Because of a large rock’s volume, it will A.weather unevenly. B.weather relatively quickly. C.not weather at all. D.weather relatively slowly.

Quick Check 9. What is the average weather condition in an area over a long period of time called? _______________

Quick Check 10. Chemical weathering such as oxidation occurs more quickly in a climate that is ___________ and ________________

Quick Check 11. Weathering occurs faster at high elevations because of A.an increase in wind but not ice or rain. B.an increase in ice and rain but not wind. C.a decrease in wind, ice, and rain. D.an increase in wind, ice, and rain.