Download Chapter Pages... 4 ..... 21 landform patterns and processes

Page 1 of 13
Chapter 1
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
Chapter
Pages... 4 ..... 21
landform patterns and processes
Chapter outline:
Introduction
A. The Structure of Earth
B. Structures on Earth’s Surface
C. How Landforms Change
(C - 1) Patterns of Plate Movement
D. Mountain Building
(D - 1) Fold Mountains
(D - 2) Mountains formed by Faulting
(D - 3) Mountains formed by Volcanoes
E. The Threat of Landform Changes
(E - 1) The threat of Earthquakes
F. Case Study
Introduction: Think!!!!!
- What would you see from space looking back at earth
* Continents
* Oceans
* Rivers
* Glaciers
* Mountain Chains
* Valleys
* Plains
* Inland seas and lakes
- Over millions of years earth has changes
* Continents have moved forming mountains and valleys
* Molten rock has poured out from within the earth
* Mountains have formed, eroded and valleys have been filled in.
Page 2 of 13
Chapter 1
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
A.
The Structure of Earth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4
fig.1.2
- The earth can be divided into distinct structural zones / eg. Inner & Outer core
- Surface features can be readily seen / eg. Mountains, Plains, Valleys..etc
- Internal features have to be studied indirectly
- Term: Seismology
The study of earthquakes and other earth movements such as those
that may be caused by human beings.
- Seismologists have developed instruments that enable them to follow the path
of earthquake waves through earth’s interior.
- Computers are used to create pictures of distinct zones within the earth.
(each zone has its own density and temperature)
- Seismologists have discovered the following structural information
about earth’s interior.
Think!!!!. . . . . . . . . . . . . . . . . . . . . . . . . . . . by way of the crow
Newfoundland.....to.....Vancouver Island
3800 miles [approx.]
6100 kilometers [approx.]
7323 kilometers Road Distance
St. John’s .....to.....Toronto
1300 miles [approx.]
2100 kilometers [approx.]
3141 kilometers Road Distance
Page 3 of 13
Chapter 1
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
Fig. 1.2
Zone/Boundary
Thickness
Features
Inner core
2700 km
(In diameter)
* solid
* made mostly of iron, with lesser amounts
of nickel
* temperature of 4000 to 6000 degrees C.
Outer core
2300 km
*molten , i.e., liquid
*made mostly of iron and nickel
*temperature above 4000 degrees C.
Mantle
2900 km
* divided into lower and upper layers
*moderate density; largely solid except for
the upper 200-300 km of upper layer,
called the asthenosphere
* the asthenosphere is in a plastic state,
sometimes acting like a liquid
* made mostly of magnesium and iron
silicates
* boundary between mantle and lithosphere,
at which earthquake waves abruptly
change speeds
Mohorovicic
Discontinuity
Lithosphere
1 - 100 km
* lowest density; solid and rigid
* made up of the lightest elements and
compounds(mostly magnesium,
aluminum, and iron silicates such as
granite)
* can be divided into two layers, one under
ocean basins (sima) and one making up
continents(sial)
* rocks of continents are also referred to as
crust
*crust is 6 - 70 km thick
Page 4 of 13
Chapter 1
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
Quick Facts
* oldest known rock on earth is found in Canada
* estimated to be 3.96 billion years old
[Precambrian time] Nunavut, NWT, Quebec,
Labrador, Ontario, Manitoba,
* found in the Northwest Territories.....?????
- The Lithosphere (zone of the earth’s surface) is made up of two main materials
Î minerals Ï rocks
- Minerals are natural chemical compounds made up of a combination of elements.
- Over 2000 minerals have been identified.
- Fewer than 30 are widely deposited and make up of the earth’s crust.
- Two of the most common elements in minerals are oxygen and silicon.
- Minerals mixed together from rocks.
- Physical and Chemical processes may be involved in creating rock
(1) Igneous Rock forms when:
- magma or lava cools and crystallizes
- takes place near volcanic eruptions
(2) Sedimentary Rock forms when:
- small particles merge and cement together
- when rivers transport pebbles, sand, rock fragments
and other debris into lake or sea beds.
- bottom layers because of pressure are cemented together to form rock.
(3) Metamorphic Rock forms when:
- already existing rock, under great heat and pressure, is transformed
(The chemical composition is altered) producing a new rock.
Quick Facts
* Highest point on earth...Mount Everest 8848 m above
sea level
* Lowest point on earth.....Challenger Deep in the
Marianas Trench 11,034 m below sea level
See fig. 1.3 ............ Ten most common elements composing earth’s mass.....pg. 6
Questions.....Page 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . # 1, 2, 3,
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Chapter 1
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
B.
Structures on Earth’s Surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 6
- Earth has a variety of landforms resulting from billions of years of geologic
change.
- Earth has been change through wind, water, ice, waves, earthquakes
and volcanic activity.
- Term: Topography: The natural and human features of Earth’s Surface.
- The most common Topographical Features of the earth are:
Î Mountains
Ï Valleys
Ð Plains
Ñ Plateaus
** Valleys : Lowest points on the Earth’s Surface (Depressions in Earth’s Crust)
Fig. 1.4
Types of Valleys:
Type
Characteristics
V-shape
* formed by river erosion
Flat-bottom
* formed by river erosion
U-shape
* formed by glacial erosion
Rectangular
with steep sides
* formed by faulting or folding
** Plains: Level tract of land
- frequently found along coastal areas or low elevations
e.g., river valleys, flanks of mountains
- gentle slope
- no local relief for thirty meters or more
Fig. 1.5
Types of Plains
Type
Characteristics
Alluvial
formed by river action
Lacustrine
were once the beds, or bottom
surfaces, of lakes which today no
longer exist
Outwash
created by sediment washed out of
melting glaciers
Page 6 of 13
Chapter 1
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
Colorado Plateau
** Plateaus:
- an extensive, relatively flat upland area
- area of flat land that has been raised upward
- often found on the interior of continents
- sometimes located within or between mountain ranges
Interior Plateau
located between the Rockies and the
Columbia mountains
- often are eroded by rivers and have a more rugged appearance
than plains.
** Mountains and Hills
- highest relief landforms on earth
- “hills” are the smaller of the two (<300 meters)
- mountains are the tallest of the two (> 300 meters).....See Definition
*occurs in long lineal chains called “ranges”
*often found on the margins of continents
* rock layers are often badly deformed (Tectonic Activity)
* Eg: Rocky Mountains / Sierra Nevada.....North America
Andes Mountains.....South America
Pyrenees.....Europe.....Spain / France
Alps.....Europe.....Italy / Switzerland
_ Discuss
Questions.....Page 7.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . #’s 4, 5, 6, 7
Worksheets 3200. . . #’s 1,2,3
Page 7 of 13
Chapter 1
C.
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
How landforms change. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pg. 10
- Alfred Wegener (German Meteorologist) in 1924 suggested that the Earth’s
Continents were once joined in a single land mass..........”Pangaea”
- 200 million years ago it broke into two sections Î Laurasia Ï Gondawanland
- The continents continued to divided and are still dividing to this present day.
- His theory was discounted for years because it was incomplete
- He presumed the forces were related to those of volcanic activity, but could not prove it
- In the 1960's J. Tuzo Wilson (Canadian) resurrected Wegener’s theory when he
noted that volcanic activity took place at the mid ocean ridges.
- Wilson also noted that rock layers on either side of the ridges were remarkable similar:
a. Age matches
b. Magnetic imprints
- Wilson theorized that the new ridges split apart the ocean floor and pushed the
continents apart.
- This separation of the ocean floor crust was termed “Sea-Floor Spreading”.
- Over the past few years it has been verified by
Î satellite photography,
Ï measurement of Seismic Activity, and
Ð study of rock and fossils.
- The large land areas (continents and ocean floor) are called “plates”
- The movement of the Plates is called “Plate Tectonics” (fig. 1-10)
Old Text
Extra Info . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Theory of Continental Drift
C-1
Patterns of Plate Movement
1. “Compressional Force”: when plates move toward each other, this caused rock
layers to bend, warp, push up and down.
2. “Tensional Force: plates break apart and move away from each other causing
the rock to sink or drop.
Questions.....Pages 10 - 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . # 8, 9, 10, 11,
Worksheets 3200. . . #’s 4,5,6
Page 8 of 13
Chapter 1
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
D.
Mountain Building.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pg
- Most mountain ranges are on the margins of continents.
- Continental plates lie long side oceanic plates and are compressed these rock layers are squeezed upward producing mountains.
- Types of Mountains Î folded mountains
Ï faulted mountains
Ð volcanic activity
D-1
Folded Mountains: (see fig 1.12 / p.13)
- rocks are bent, buckled and pushed upward in a folding pattern.
- caused from compressional forces.
- simple folds resemble a wave pattern (Anticline-upfold / Syncline- downfold)
D-2
Faulted (Faulting) Mountains: (fig. 1.13)
- Caused by tensional and compressional forces.
- Compressional Forces cause the rock to fracture or break.
- Tensional Forces separate the rock causing fractures or breaks.
- Fractures may be shallow or deep into the earth’s crust.
- Fractures may also be short or long (hundred of kilometers)
- Faulting may cause some rock to move up while others drop (some fault)
Normal fault: plate on one side drops down lower than the other side.
Rift Valley: two normal faults occur and the center drops (tension). . .
Block Mountain: two normal faults occur and the center is pushed
up (tension). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reverse fault: fault occurs and one block is pushed over the other
(compression).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overthrust fault: same as reverse fault only rocks were folded prior
to the fault.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B
D
E
C
A
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Chapter 1
D-3
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
Volcanic Activity Mountains
- Plates push against each other and create intense heat and pressure and
the decay of radioactive materials.
- The intense heat melts the rock beneath the crust changing it to magma
- The magma flows into cracks and fractures.
- If the magma does not reach the surface and fills the cavities between rock
it is called Intrusive Rock.
- After erosion takes place the more resistant rock is left behind
- if the magma reaches the surface it is termed extrusive volcanic activity.
- Liquid rock is called lava.
- Small molten rock fragments and gas is called “ash” or “cinders”
- Depending on the amount of gas and the chemical composition of the lava,
a volcano can be violent or quite calm.
- Mild volcanic eruptions are characterized by
thin liquid lava flows and
small amounts of gas.
- Explosive eruptions are characterized by
thick lava flows and
large amounts of gas, ash and cinders.
- Thick lava may solidify and plug the opening, this pressure builds and
finally the trapped material explodes.
- Volcanoes that we see are caused by extrusive volcanic activity .
- A single opening in a volcano is called a “Vent”
Page 10 of 13
Chapter 1
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
Types of Volcanoes:
Ash-and-Cinder cones: [a]
* explosive in nature
* thick slow flowing, rapidly solidifying lava
* symmetrical in shape
* steep sides
* large crater
Shield Cones: [c]
* mild eruptions
* little or no ash and cinders
* very thin liquid lava
* broad base
* flat cones
Composite Cones: [b]
* alternating violent eruptions and other times quiet activity
* has a layer of ash and cinders intermixed with layers of lava
* weak points may develop along the sides
* lava flows out of these weak points to form smaller cones (Conelets)
- Volcanoes may sometimes develop along long cracks and
fractures as opposed to a single vent.
* typically characterized by lava flowing on both sides of the fracture
or fissure
* lava may flow over great distances
* may cause extensive flat areas called lava plateaus
* sometimes gently rounded areas may form called lava domes
Questions.....Pages 14 - 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . #12, 13, 14, 15, 16, 17,
Worksheets 3200. . . . . #’s 7,8,9,10,11
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Chapter 1
E.
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
The Treat of Landform Changes:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pg
- People have always been fascinated by the power of nature.
- Thousands of people are affected by natural disasters.
- Natural disasters are directly related to forces operating in the Earth’s Crust
and on Earth’s surface.
- Natural disasters often spark chains of related, interacting events that
further challenge the people involved
E-1
The threat of earthquakes .....(pg. 19)
- Another threat posed by moving plates is that of earthquakes.
- Earthquakes are more devastating in underdeveloped countries than in
developing countries.
Underdeveloped countries
First - Developing countries have a higher population density in earthquake zones.
- Buildings in developing countries are substandard.
Second - Resources and relief plans for the earthquake aftermat is very limited.
Developed Countries:
First - Buildings in earthquake zones are being made “earthquake proof”.
Second - Special earthquake emergency response plans are drawn up.
Note: Special precautions, however, do not always prevent major catastrophe.
points to consider
Page 12 of 13
Chapter 1
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
The following case study describes in detail the unfolding of a volcanic disaster.
Case Study
Mount Pinatubo Volcanic Eruption, Philippines, 1991
** Explosive types of volcanic pose the greatest natural hazard for people,
if little advance warning is given
Setting the Stage
- Located l00 km northwest of the Capital of Manila
- Composite cone in nature (ash-and-cinder / layers of lava)
- Elevation of 1745 m before erupting.
- Among the highest peaks in its chain of volcanic mountains
- Last erupted 600 years ago.
- Slopes covered with vegetation.
- Surrounding area heavily populated.
- 15,000 people lived on its flanks.[sides]
- 500,000 people lived on alluvial fans surrounding the volcano.
- Concentrations of population partly due to fertile volcanic soil.
- Air Force Base and Naval Station near by.
Act One
- Unrest first noted April 2, 1991 (steam explosions)
- Precursors or indicators of impending volcanic activity were established
- Danger zones were prepared
- 58,000 people were evacuated.
- Including 15,000 from Air Force Base.
- Over 10 week period..... 100,000 people were evacuated.
Act two
- Signs of volcanic activity continued for approximately 2 months.
- June 12 - blast of volcanic ash, 19,000 meters was sent skyward.
- June 15 - Lateral eruption creates a 2 km crater on the north side
of volcanic dome.
- Ash, Cinders, and lava flows..... cover 100 km2
- Many of the monitoring devices were destroyed.
- Same day of eruption ........Typhoon sweeps through island.
- Remaining military and scientific personnel were evacuated.
Page 13 of 13
Chapter 1
Unit One..........Major Land and Water Forms
Landform Patterns and Processes
Act Three
- Ash and Cinders were given off for several days.
- Typhoon increased hazards from ash and cinders.
- Typhoon spreads ash and cinders over 20,000 km2
- Crops were damaged.
- Buildings were destroyed.
- Transportation routes blocked.
- 330 deaths- when buildings collapsed - under wet Ash and Cinders.
- Rainfall resulted in mudflows.
- Homes and bridges destroyed well beyond the volcanic cone area.
- Crops and croplands were lost.
- Porac River rose approximately one meter from rain and ash.
- Mudflows continued through the wet season ..... July
- By August 100,000 people still could not return home.
- Some people could never return.
- Homes were buried under meters of ash and mud.
The Aftermath
- Immense quantities of dust, ash, sulphur dioxide and other gases
filled the atmosphere.
** Potential long term effects on the “world”.
- Weather patterns were altered over the next several years.
- Average global temperature dropped by ½ degree.
- Ash and gas moves around the earth for several months (brilliant sunset)
- Water droplets and sulphur dioxide joined to increase and acid rain problems.
- Sulphur dioxide was so high in the atmosphere that it will probably
remain their for many years.
Questions.....Pages 19 - 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . # 18, 19, 22,
Worksheets 3200. . . #’s 12, 13,14, 15, 16, 17, 18