1. Science Starter

2. Running Water
Chapter 6, Section 6.1

3. Looking Back Mechanical and Physical Weathering Soil
Soil Profiles/Types
Mass Movements

4. STUDY STUDY STUDY STUDY
Looking Ahead
Tomorrow we will start 6.2 & 6.3
TURN IN YOUR WORK
Report Cards October 15
Test Chapter 5 & 6 on 10/21
This means that we will NOT have review but there will be chances for points
Vocabulary Quiz Ch /14
STUDY STUDY STUDY STUDY

5. Today’s Plan
Notes on 6.1 & 6.2
Water Cycle Foldable Activity

6. Let’s Review What are mass movements classified by?
Kind of material that moves, how fast it moves, and how it moves.
What are the main reasons mass movements happen?
Oversteepening of slopes, removal of vegetation, saturation of soil, Earthquakes.
What is the main influence on mass movements?
Gravity
What is the slowest mass movement? The fastest?
Creep = Slowest, Slides = Fastest

7. Chapter 6 Vocabulary Water Cycle Infiltration Transpiration Gradient
Stream Channel
Discharge
Tributary
Meander
Bed Load
Capacity
Delta
Natural Levee
Floodplain
Karst Topography
Sinkhole
Flood
Drainage Basin
Divide
Zone of Saturation
Groundwater
Water Table
Porosity
Permeability
Aquifer
Spring
Geyser
Well
Artesian Well
Cavern
Travertine

8. Introduction Water is everywhere on Earth!
Oceans
Glaciers
Rivers
Lakes
Air
Soil
Living Tissue
Makes up the Earth’s hydrosphere.
97.2% of water is in oceans
Ice and Glaciers are 2.15%
0.65% is atmosphere, lakes, streams, and groundwater.
THIS IS THE WATER WE RELY ON

9. Water Breakdown Demonstration

10. The Water Cycle

11. The Water Cycle
Water constantly moves among the oceans, atmosphere, solid Earth, and the biosphere.
Unending cycle called “The Water Cycle”
Cycle is possible because water readily changes from one state of matter to another (solid, liquid, gas) at temperatures and pressures COMMONLY FOUND at Earth’s surface.
Worldwide system powered by energy from the sun.
Atmosphere provides the most important link between the oceans and the land.

12. Water Cycle Wind transports moisture until they condense into clouds.
Precipitation (rain and snow) falls to earth.
Water that falls into ocean has completed the cycle and starts over.
Water that falls on land must make it back to the ocean to complete the full cycle.
What happens to precipitation that falls on land?
Some of it is absorbed into the ground through infiltration.
Infiltration is the movement of surface water into rock or soil through cracks and pore spaces.
Water gradually moves through land and seeps into lakes, streams, or the ocean.

13. Water Cycle
When the rate of rainfall exceeds the Earth’s ability to absorb it, the excess water flows over the surface into lakes and streams.
Called runoff
Much of the runoff returns to the atmosphere because of evaporation from soil, lakes, and streams.
Plants also absorb water and release it into the atmosphere through transpiration.
When precipitation falls in cold areas (high elevation or latitude) water may not immediately soak in, run off, or evaporate.
Might become part of a glacier.
Glaciers store large amounts of water on land.

14. Glacier Melt
If ALL present-day glaciers were to melt and release all their water, ocean levels would rise by several dozen meters.
Greater distance over a slope than a steep increase in elevation.

15. Glacial Melt

16. Glacial Ice Melt

17. Glacial Melt

18. Glacial Ice Melt

19. RAINFALL RATE = EVAPORATION RATE
Earth’s Water Balance
Earth’s water cycle is balanced.
Balance in the water cycle means that the average annual precipitation (the amount of precipitation that falls in one year) over the entire Earth equals the amount of water evaporating.
RAINFALL RATE = EVAPORATION RATE
Precipitation > Evaporation on land BUT
Evaporation > Precipitation over ocean
System is balanced because the world’s ocean level would not change that much (assuming no other input).

20. Streamflow
Gravity influences the way water makes its way to the oceans.
Streams and rivers carry water downhill from the land to the sea.
Time it takes depends on the velocity of the stream!
Velocity = distance/time
Slow streams flow at less than 1km/hr, while fast streams can exceed 30km/hr
Along straight stretches of stream the highest velocity is near the CENTER of the stream channel just below the surface of the water.
This is where friction is SLOWEST so water can move FASTER.
Zone of maximum speed shifts to its outer bank when a stream curves.

21. River Profiles

22. Streamflow
The ability of a stream to erode and transport materials depends largely on its velocity.
Moving fast = can carry a lot
Moving slow = cannot carry a lot
Factors that influence the velocity of a stream:
Gradient of Channel
Shape of Channel
Size of Channel
Roughness of Channel
Discharge

23. Gradient Gradient is the slope/steepness of a stream channel.
Expressed as …. Vertical drop/distance
Some parts of the Mississippi have low gradients of 10cm per km or less.
Mountain streams tumble downhill at a rate of more than 40 m/km
Mountain stream gradient is 400x greater than the lower Mississippi
Gradient varies over a stream’s length.
Steeper gradient = more energy the stream has as it flows downhill.

24. Stream Gradient
WHAT MATHEMATICAL FORMULA DOES THIS REMIND YOU OF?

25. Channel Characteristics
Stream channel is the course the water in a stream follows.
Water flows and encounters friction from the sides and bottom of channel
Slows its forward movement
Shape, size, and roughness of the channel affects the amount of friction.
Ex: An irregular channel filled with boulders creates enough turbulence to slow the stream significantly.
Water in a smooth channel flows more easily.
Larger channels also have more efficient water flow because less water is in contact with the channel surface.

26. Discharge
Discharge of a stream is the volume of water flowing past a certain point in a given unit of time.
Measured in cubic meters per second (m3/s)
Discharges of most rivers change with rainfall and snowmelt.
Size and velocity of stream also changes when discharge changes.
Stream channel widens and deepens to handle additional water.
As size of channel increases, there is less friction and water moves more swiftly.

27. World’s Largest Rivers (Discharge)
Rank
River
Country
Average Discharge (m3/s) 1
Amazon
Brazil
212,400 2
Congo
Zaire
39,650 3
Yangtze
China
21,800 4
Brahmaputra
Bangladesh
19,800 5
Ganges
India
18,700 6
Yenisei
Russia
17,400 7
Mississippi
United States
17,300 8
Orinoco
Venezuela
17,000 9
Lena
15,500 10
Parana
Argentina
14,900

28. Changes from Upstream to Downstream
One useful way to look at a stream is to look at its profile.
A profile is a cross-sectional view of a stream from its source (headwaters) to the mouth.
Mouth is the point downstream where the river empties into another body of water.
Most obvious feature of a typical stream profile is a decreasing gradient or slope from its headwaters to its mouth.

29. Changes from Upstream to Downstream
Gradient decreases between a stream’s headwaters and mouth, DISCHARGE INCREASES.
Amount of discharge increases because more and more tributaries enter the main channel as it makes its way downstream.
A tributary is a stream that empties into another stream.
In humid regions, groundwater supply adds even more water.
As river moves downstream, the width, depth, and velocity change with the increased volume of water the stream carries.

30. Changes from Upstream to Downstream
Increase in average velocity of water downstream contradicts what people way think about mountain streams.
Most people think mountain streams are fast and lowland rivers are slow.
Mountain stream LOOKS fast and violent, but its average velocity is often LESS than the average velocity of a river at its mouth.
Difference in velocity is due to the great efficiency of the larger downstream channel.
Headwaters: Steep Gradient, small channel, many boulders.
Mouth: Lower gradient, large channel, small particles

31. Base Level
Two types:
Ultimate
Temporary
Sea Level is the ultimate base level because it is the lowest level that stream erosion can lower the land to. Can’t go any lower than the ocean!
Temporary base level includes lakes, resistant layers of rock, and main streams that act as a base level for their tributaries.
Stream enters a lake, velocity = 0. No erosion is happening.
Lake prevents stream from eroding below its level at any point upstream from the lake.
Outlet of lake can cut downward and drain the lake, the lake is only a TEMPORARY OBSTACLE in the stream’s ability to erode its channel and reach the ocean.

32. Base Level

33. Base Level
A stream in a broad, flat-bottomed valley that is ear its base level often develops a course with many bends called meanders.
If base level dropped or the land was uplifted, the river (which would then be above base level) would have excess energy and would downcut its channel.
Incised meanders—a winding river in a steep, narrow valley.
THE GRAND CANYON.

34. Let’s Review How is Earth’s Water Cycle balanced?
The amount of precipitation equals the amount of evaporation.
Where is most of Earth’s water located?
In the Oceans
How do gradient and discharge change between a stream’s headwater and its mouth?
Stream’s velocity is the most influencing factor.
What would happen if evaporation exceeded precipitation over the continents and oceans?
The Earth’s surface and oceans would start to dry up.
How does the development of urban areas along streams and rivers affect discharge during periods of heavy rainfall?
Increased magnitude and frequency of floods.