Changing Changing Earth And Earth And

OceansOceans

1. Earth’s lands and oceans can be affected by NATURAL PROCESSES, or events that occur naturally in the environment. Some of these processes occur SLOWLY while others are rapid processes. We can also classify these processes according to whether they are created from CONSTRUCTIVE or destructive forces.

2. The natural processes we will be concerned with in this unit are: WEATHERING, erosion, DEPOSITION, landslides, volcanic eruptions, EARTHQUAKES, and floods.

3. Classifying the natural processes that affect Earth’s lands and oceans:

RAPID SLOWLANDSLIDES WEATHERING

VOLCANIC ERUPTIONS

EROSION

EARTHQUAKES DEPOSITION

FLOODS

CONSTRUCTIVE DESTRUCTIVE

DEPOSITION WEATHERING

VOLCANIC ERUPTIONS

EROSION

FLOODS LANDSLIDES

EARTHQUAKES

FLOODS

4. Destructive forces are those that DESTROY landforms. They change the surface of the earth by WEARING IT DOWN.

5. Weathering is the process where rocks and minerals near the surface of the earth are BROKEN DOWN, dissolved, or decomposed into smaller pieces. It can SMOOTH the edges of rocks and wear down the peaks of mountains. It can also be affected by:

a. HARDNESS of the rocks (what it is made of)

b. SLOPE of the land

c. Exposure to sun and RAIN / WATERd. Climate or TEMPERATURE

6. Weathering can be considered PHYSICAL (a.k.a. mechanical) or chemical.

7. Physical (MECHANICAL) weathering only changes the SIZE / SHAPE of the rock. It does not change the rock’s composition, or WHAT IT IS MADE OF. It can be caused by three things:

a. Temperature change- rocks EXPAND in the summer and contract in the winter

b. Frost wedging (a.k.a. frost ACTION)- when rainwater gets into a crack, the water FREEZES. When it freezes, it EXPANDS and breaks the rock.

c. PLANT roots- they break right through the rock.

8. Chemical weathering changes the SIZE of the rock BUT ALSO changes the rock’s COMPOSITION. It can be caused by two things:

a. The air we breathe- water and air change iron into RUST [called iron oxide= oxygen (O2) + iron (Fe)]

b. CARBONIC acid dissolves the rock- when CO2 in the air dissolves with rainwater/groundwater, it forms a weak acid called carbonic acid (a.k.a. carbonated water)

9. Caves and caverns are formed when rocks dissolve forming hollow areas.

• stalactites- hang from the CEILING

• Stalagmites- up from the GROUND

c. columns- where they both MEET

d. They are formed from rock made mostly of calcite or LIMESTONE, which is easily worn away by carbonic acid.

Column

Stalactite

Stalagmite

10. Erosion- the process of CARRYING away (or transporting) weathered materials like rocks, minerals, and soil. These materials are carried away by WIND, water, and gravity.

11. Agents of erosion are the FORCES that carry out erosion. Common agents of erosion include:

a. Water- the most COMMON. It carries materials such as soil, sand, and pebbles.

• Water breaks, ROUNDS, and polishes rocks

• The distance water carries rocks depends upon the SIZE of the particles and the FORCE of the water.

• It forms a “V” shaped valley between mountain peaks.

• Can form DELTAS when it drops the sediment because it is unable to CARRY it anymore.

• WAVES AND TIDES also erode the land

• The GRAND CANYON is an example of a landform being created from water erosion, thanks to the COLORADO River over many years.

b. Glaciers- moving masses of ICE

• As gravity pulls ice DOWN the mountain, rocks and soil are pushed, DRAGGED, or carried with it.

• They form a “U” shaped valley from the original “V” shaped one.

• As they melt, they DROP the rocks and soil they were carrying at one time (called its LOAD).

• They actually formed the GREAT LAKES

(remember “Homes”)

c. Gravity- eroded materials tend to move to LOWER elevations because gravity pulls them DOWN

d. Wind- the WEAKEST agent

• It is only moving air and can only pick up SMALL particles of rock and topsoil. Obviously, it it’s a stronger amount of wind, more materials can be picked up.

e. Human activity- we can INCREASE the speed of destructive forces

• Cutting down TREES- roots can’t keep the soil in place and increases erosion. So roots help reduce erosion.

• Air pollution from factories and CARS increase weathering.

• MINING or digging into the land

12. Landslides- SUDDEN mass movements of land downhill due to gravity

• They can cause BUILDINGS to fall or power lines and gas lines to break

• They can even occur on the continental slope in the ocean

13. Earthquakes- VIBRATIONS on the Earth’s surface caused by a sudden movement or release of ENERGY in Earth.

a)They are often found along a FAULT, or a break in the Earth’s surface

b) Some cause little DAMAGE and some cause LOTS of damage

c) Large EARTHQUAKES can cause landslides

d) When they occur under the ocean, huge waves are created (called TSUNAMIS) and can destroy land and cause great damage if the waves come ashore.

e) SEISMOGRAPH is an instrument that measures vibrations inside the earth. By observing these vibrations, scientists may be able to predict when they occur

f) When inside during an earthquake, get under a STURDY table. Avoid being near windows because they may shatter.

g) If outside, quickly move to an OPEN SPACE and avoid trees, power lines, or buildings that could fall on you.

h) Be prepared! Make a SURVIVAL kit (water, batteries, flashlight) and practice (drills).

i) Scientists are now investigating ways to make buildings earthquake-PROOF

14. Floods- occur when LARGE amounts of water cover land that is usually DRY.

a) Heavy RAIN or quickly melting snow can cause water to flow OVER the land (flood).

b) When the flood occurs, rapid EROSION can take place and move soil and sediments away.

c) When the flood RECEDES (goes back), new sediment is left behind and can BUILD up rich soil deposits.

15. Constructive forces are those that CREATE landforms. They BUILD UP the Earth’s surface. These forces include DEPOSITION, volcanic eruptions, and floods.

16. Deposition- the dropping (or DEPOSITING) of sediments by water, wind, or ice.

a) It BUILDS UP new land on the surface of the earth, like a DELTA at the end of a river or a pile of sand (sand DUNE) in the desert. It also builds up beaches and river banks.

b) SHELLS on the beach are evidence of deposition by ocean waves.

17. Volcanic eruptions can change the Earth’s surface:

a) Volcanoes are MOUNTAINS with openings in the Earth’s crust where magma, gases, and ash reach the surface

b) When magma reaches the surface it is called LAVA. As the lava eventually cools, new land (mountain) is created. The HAWAIIAN Islands are examples of how volcanic eruptions have created new land.

c) When the magma erupts from the volcano, the top of the mountain can be changed.

d) Lava and ASH can destroy forests and bury fields.

e) Volcanic eruptions can even change weather patterns.

f) When volcanic mountains are formed under water, they are called SEAMOUNTS.

g) The RING OF FIRE is the area where most volcanic activity occurs.

18. The ocean has many geologic landforms.

a) Continental shelf- where the edges of the continent slope own from the SHORE into the ocean. It is the part of the continent located UNDER the water. Abundant fishing is found on the shelf.

b) Continental slope- where the shelf drops to the BOTTOM of the ocean floor. The depth of the ocean water increases greatly here.

c) Mid Ocean Ridge- an underwater volcanic MOUNTAIN range on the bottom of the ocean which divides the ocean floor into two parts.

North America

South America

Africa

d) Rift zone- a TRENCH in the center of the highest part of the mid-ocean ridge.

e) trenches- steep-sided CANYONS and deep, narrow valleys in the bottom of the ocean. They are the deepest part of the ocean basin and are deeper than any valley on land.

f) Ocean basin- located on either side of the mid-ocean ridge. It is made up of low HILLS and flat PLAINS and are the deepest part of the ocean. It is also known as the ocean FLOOR, abyssal plain, and ocean plain.

19. Earth is made of SOLID land. Some of the land is located above the Earth’s water and some is located below the oceans. Even so, there are similarities and differences between landforms found in these two areas:

Continental Landforms (above water)

Oceanic Landforms (below water)

CANYON TRENCHES

VALLEY RIFT ZONE

VOLCANO SEAMOUNT

MOUNTAIN RANGE MID-OCEAN RIDGE

LOW HILLS OR PLAINS

OCEAN BASIN AND PLAINS

Labeling ocean floor adobe file

20. The area where the ocean meets the land is called the OCEAN SHORE ZONE.

a. It has specific features that can be affected by WAVES, currents, tides, and storms (like hurricanes).

b. BEACHES, barrier islands, estuaries, and inlets are all affected by natural processes like those mentioned above.

21. Beaches- the sandy area on the coast (or shoreline) where the land meets the ocean.

a. They are changing because of WIND AND WATER.

b. WAVES can wear away the land and expose a rocky shore. They can also deposit SAND along the shore, forming a beach.

c. If the waves reach the beach at an ANGLE, the sand is moved along the coast.

d. Currents (called LONGSHORE currents) along the shoreline can move sand from one location to another.

e. TIDES can bring in sand, shells, and ocean sediments at high tide and leave them behind at low tide.

22. Barrier Islands- with sandy beaches that are SURROUNDED by water on all sides.

a. They occur naturally and help PROTECT the mainland from the effects of waves on its shore.

b. As waves deposit SAND on the beaches, the shape of the barrier islands change.

c. CURRENTS can move sand from one end of the island to another.

23. Estuaries- the area where a RIVER meets the ocean They have a mixture of FRESH AND SALT water.

a. WAVES can deposit sand in the estuaries.

b. At high TIDE ocean water brings in sediments and sea life that feed and provide nourishment for the estuary.

24. Inlet- water-filled spaces BETWEEN barrier islands.

a.As the tides change, the amount of WATER in the inlet will change.

b.Ocean currents and STORMS can change the shape of an inlet opening.

25. Water on Earth can be moved in various ways:

a. WAVES- the repeated movement of water.

• Its highest part is called the CREST and lowest part is called the TROUGH.

• Most are caused by WINDS that blow across the water’s surface.

• They can change their shape when they reach the shore.

•Tsunamis are examples of giant TIDAL waves caused by underwater EARTHQUAKES.

b. Currents- FLOWING streams of water that move continually through the ocean in a specific direction. They can be on the SURFACE of the ocean or deep in the ocean.

• Surface currents flow at the top due to the force and direction of the WIND and the Earth’s movement. They flow along CURVED paths.

•Warm surface currents are driven by the Earth’s rotation from TROPICAL to higher latitudes.

•Cold surface currents are driven by the Earth’s rotation from the POLAR latitudes toward the equator.

c. TIDES- the rise and fall of waters in oceans and seas which change the LEVEL of water at the shoreline.

• They are caused by the pull of the Moon’s GRAVITY on Earth.

• High (FLOOD) tides occur when the water level is at its highest point.

•Low (EBB) tides occur when the water level is at its lowest point.

•Tides rise and fall about TWICE a day (about every 6 hours).

• Neap tides occur when the sun and moon are pulling on the Earth at RIGHT angles. The result is that there is LITTLE difference between high and low tides.

• SPRING tides occur when the sun and moon are IN LINE with the Earth. We get higher high tides and lower low tides at this time.

26. Human activities can HELP the land and ocean preserve the resources that these areas provide. The wise use of natural resources is called CONSERVATION.

a. The 3 R’s: REDUCE (use less of), reuse (use again), and RECYCLE (make a new product from old materials).

b. Clean-up projects (litter pick-up, Beach Sweep).

c. Putting up fences or wind BREAKS to prevent erosion

d. Creating JETTIES along beaches to keep sand from washing away.

e. Planting TREES, bushes, and grass to improve air quality and keep erosion from carrying away the soil.

f. Crop ROTATION (changing crops from year to year).

g. COMPOSTING

27. Human activities can also HARM the land and oceans by causing resources to be DAMAGED or destroyed. Pollution is anything that HARMS the natural environment.

a.Dumping materials into RIVERS (which eventually flow into estuaries and oceans)

b. LITTER pollutes land and water.

c. Landfills for our TRASH can leak into groundwater

d. SMOKE from cars, factory fumes, and burning fuels pollutes the air (acid RAIN, smog).

e. OIL SPILLS harm the ocean and can cause life there to be killed.