1. The creation of sedimentary rocks
Erosion & Deposition
The creation of sedimentary rocks
The three types of rocks created by the rock cycle are igneous, metamorphic and sedimentary
Metamorphic rocks are created by heat & pressure, while igneous are primarily created by melting solid rock into liquid rock called magma, & then cooling that rock either above or below ground
In the rock cycle, sedimentary rocks are created by weathering, erosion, cementation and compaction
This PPT discusses the erosion aspect of sedimentary rock creation
Erosion often involves water
Water will erode the land and it will change the shape of the land
This PPT explains how water, which is a surface process, participates in this aspect of the rock cycle

2. Weathering and Mass Movement
Objectives:
1. Describe the processes by which erosion wears down and carries away rock
2. Distinguish between chemical and mechanical weathering
3. Describe the factors that affect the rate of weathering
4. Explain how the force of gravity contributes to erosion by mass movement

3. Erosion
Definition: erosion is the process that wears down and carries away rock and soil
Erosion is associated with movement from one place to another
Erosion acts through weathering, the force of gravity, and through movement of streams, groundwater, glaciers, wind and waves
Erosion breaks down the tallest mountains over time

4. Weathering
Definition: weathering is the process by which rocks are chemically altered or physically broken down into fragments at or near Earth’s surface
There are 2 types of weathering: mechanical and chemical
Both processes cause rocks to disintegrate and decompose
Definition: mechanical weathering is the process of physically breaking rock into smaller fragments
In this picture, wind and water in the form of precipitation such as rain are working on these rocks
The top layers of the rock will flake off and over time will continue to break into smaller and smaller pieces
Ultimately, rocks break down to become the soil under our feet

5. Definition: frost wedging is physical weathering due to water seeping into cracks and expanding due to freezing
Many road potholes are the result of frost wedging
Definition: abrasion is physical weathering caused by the process that occurs when rocks scrape or grind against each other
This can occur by water or wind

6. Plant roots cause physical weathering by growing into cracks breaking rocks apart
Erosion causes physical weathering by removing material from the surface of the rock, releasing pressure on the rock causing the outside to crack and flake
Definition: chemical weathering in a process in which rock is broken down by chemical reactions

7. Water is the main reactant in chemical weathering
Chemical reactions dissolve the minerals that make up the rocks or changes them into new materials
Water and carbon dioxide combine to form carbonic acid producing acid rain
Acid rainwater dissolves many minerals
Rusting, which is a kind of oxidation, occurs in minerals that are rich in iron
These rocks have a high iron content
Over time, the water, wind and sun have done their work to oxidize the iron into rust creating the red color that you see
The grey rocks are flaking due to a similar process and over time will break

8. Factors that Affect the Rate of Weathering
There are 3 main factors that determine how fast mechanical and physical weathering take place
They are temperature, availability of water and the type of rock
Certain rocks like limestone and marble undergo rapid chemical weathering since their main mineral (calcite) dissolves in water
Slate, quartz and mica are more resistant to chemical change

9. Mass Movement
Definition: mass movement is the downward movement of rock and soil due to gravity
Definition: the rapid movement of large amounts of rock and soil is a landslide
Landslides often happen after heavy rain
Definition: mudflow is rapid mass movement of soil & other sediment with water
After rain water loosens the sediment, increases its weight and causes it to flow
Our area has been susceptible to mudflow in the past
It particularly has affected Slide Mountain
Chunks of the sheer side break off from time to time
If the falling mountain side lands in a significant water source, it can create a mud slide and has done so in the past

10. Definition: creep is the gradual slowing down of soil that is moving down a slope
Creep usually occurs due to ice
Creep happens so slowly is often hard to notice
Definition: slumping occurs when weak layers of soil or rock move downslope as a single unit
Gravity acting on water saturated soil and rock causes slumping

11. Water Shapes the Land Objectives:
1. Explain how running water erodes the land
2. Identify features formed by erosion and deposition due to running water
3. Describe how caves and sinkholes are formed by groundwater erosion

12. Running Water & Erosion
Definition: deposition is the process in which sediment is laid down in new locations
Deposition is a type of erosion
Most sediment is moved by running water
Running water erodes the land
Definition: saltation is the process of particles bouncing along a stream bottom
A large amount of deposition with a fast moving water source increases erosion
Speed increases a streams ability to erode
Look closely at this picture
Erosion will wear away the river on one side, picking up those rocks & soil, and then deposit it elsewhere

13. Features Formed by Erosion
Water erosion form v-shaped valleys, waterfalls, meanders and oxbow lakes
Near its source the stream moves fast, causes valley’s sides to become steeper & sharply angled creating a V
V-shaped valleys can contain rapids and waterfalls
Waterfalls develop where a stream crosses rock layers that differ in hardness
The harder layers resist erosion for the top of the waterfall while the other layers are worn away creating the cliff over which water tumbles

14. Definition: a flood plain is the flat area along a stream that is entirely covered only during times of flood
During flooding, erosion may further widen the valley
Definition: a meander is a looplike bend in the river caused by sediment being deposited on the outside of a curve in the river
Features deposited by flowing water include alluvial fans and delta

15. Definition: an alluvial fan is sediment that has settled out as the stream flows out of the mountains creating a fan-shaped deposit
Definition: a delta is mass of sediment that was carried & deposited by a stream that flows into a lake or ocean where the water slows down
The delta is located where a river enters a large body of water

16. Groundwater Erosion
The processes of chemical weathering causes groundwater erosion including the formation of caves and sinkholes
Acid rain moves through the ground reacting with some rocks
Limestone easily erodes away forming caves and caverns
Sometimes water drips into the cavern from rock layers above
While Reno can get a rare sinkhole, usually from groundwater level, sinkholes are far more common in places like Florida where the ocean is nearby & water is flowing underneath the ground where it cannot be seen

17. Definition: a stalactite is an icicle-like formation of minerals created from water dripping from the ceiling of the cave
Definition: a stalagmite is a pillar of minerals created from water dripping down to the floor
Definition: a sinkhole is an entire portion of ground that has collapsed due to erosion weakening a layer of limestone
Areas of southern and central US have many sinkholes

18. EXAMPES OF SEDIMENTARY ROCK