Rates of Weathering Earth Science grade -9-

1. Rates of WeatheringEarth Science grade -9- Prepared by the teacher: Ronak Ahmed International Schook / Duhok

2. Why ledges exist in nature? Because the rock that the ledge is made of weathers more slowly than the surrounding rock. Weathering is a process that takes a long time. However, some rock will weather faster than other rock. The rate of weathering depend on: Climate. Elevation. The make up of the rock.

3. Differential Weathering which of these rocks weathered slower? Granite limestone Because the harder rock (granite), weather more slowly than softer rocks (limestone) What is Differential weathering? Is a process by which softer, less weather resistant rocks wear away and leave harder, more weather resistant rocks behind.

4. How this rock tower is formed? The landform that has been shaped by differential weathering. This rock tower was once a mass of molten rock deep inside an active volcano. • When the molten rock cooled & hardened, it was protected from weathering by the outer rock of the volcano. • After thousands of years of weathering, the soft outer parts of the volcano have worn away. • The harder, more resistant rock is all that remain.

5. Some spectacular landforms that forms from differential weathering Gooding city in Idaho The window in Big Bend in Texas

6. The shape of Rocks On the outer surface That mean: whenever there is more outer surface exposed to weathering, the worn down of rocks will be faster. In which part of rocks the weathering is takes place? The large rock have a large surface area. But The large rock also has a large volume Because of the large volume, the large rock will take a long time to wear down.

7. If the large rock is broken into smaller fragments Large rock Weathering of the rock happens much more quickly. Why the rate of weathering increases when the rock was broken into smaller fragments? Because a smaller rock has more surface area to volume than a larger rock has. So, more of a smaller rock is exposed to the weathering process.

9. Weathering and Climate Is the average weather condition in an area over a long period of time. What is climate? The rate of weathering in an area is greatly affected by the climate of that area. How can different climates affect on the rate of weathering? Example: This mailbox is in a dry climate and does not experience a high rate of weathering. This mailbox is in a warm, humid climate. It experiences a high rate of chemical weathering called oxidation and the result is rusty mailbox

10. Self-Check Why would a mailbox in a warm, humid climate experience a higher rate of weathering than a mailbox in a clod, dry climate? Warm, humid climates have higher rates of weathering because oxidation happens faster when temperatures are higher and when water is present.

11. Temperature and Water The Rate of Chemical weathering The Rate of Mechanical weathering Also increase the rate of mechanical weathering. The freezing of water that seeps into the cracks of rocks causes rocks to break apart. Over time, this form of weathering can break down even the hardest rocks into soil. Temperature: Temperature: Is faster in warm, humid climates. The rusty mailbox has experience a type of chemical weathering called oxidation. The more often temperatures cause freezing & thawing, the more often rocks break apart & this lead to a greater rate of mechanical weathering. Water: Water: Oxidation, like other chemical reactions, happens at a faster rate when temperatures are higher and when water is present.

12. Weathering and Elevation Mountains (like everything else) are exposed to air & water. So, its weathered down. Which rocks are more vulnerable to exposed to weathering? Rocks at high elevation, as on a mountain, are exposed to more wind, rain, and ice than the rocks at lower elevation. What is the result of more exposure to air, wind, and ice? This causes the peaks of mountains to weather faster.

13. Gravity affects on weathering too…How? How the process is occur? The steepness of mountain slopes increases the effects of mechanical & chemical weathering. • Steep slopes cause rainwater to quickly run off the sides of mountains. • This rainwater carries the sediment down the mountain’s slop. • This continual removal of sediment exposes fresh rock surfaces to the effect of weathering. Does the new rock surfaces also exposed to weathering? Yes, when gravity causes rocks to fall away from the sides of mountains forming talus

14. Self-Check Why do mountaintops weather faster then rocks at sea level? Mountains weathered faster because they are exposed to more wind, rain, and ice, which are agents of weathering.