Download WG3200 Unit 1 - Chapter 1 File

UNIT I: Land and Water Forms
UNIT I: Land and Water Forms
• Earth's Interior
– In this lesson you will learn:
• About the interior of the earth.
• It is impetrative to understand the
earth's structure before you can
understand tectonic forces.
Earth's Interior
.
• Is neither all solid nor is it all molten.
• It is made up of layers with different :
– density,
– thickness
– and composition
Earth's Crust
• is not one continuous layer.
• It is broken into many sections known as plates.
• They all float and move on top of the molten
asthenosphere.
• When they push together and when they pull
apart they create "tectonic forces".
• Note; without this liquid layer called the
asthenosphere we would not experience
earthquakes or volcanoes.
Use your text to:
• What makes up the different layers of the
EARTH :
– density,
– thickness
– and composition
Earth's Interior
Zones within the earth:(5)
1. Inner Core: The deepest part of the
earth (1512 miles deep) is a solid that
contains both iron and nickel.
It is because of this that the centre of the
earth is a magnet, a compass.
It generates a magnetic field that protects
the earth from flying out of orbit.
Earth's Interior
Zones within the earth:(5)
2.Outer Core: Outside of the inner core lays
the outer core (1419 miles deep).
This is much like the inner core with the
exception that it is a liquid.
Contains sulphur and oxygen (which lowers
the melting point).
Earth's Interior
Zones within the earth
3. Mantle: Occupying 1789 miles of the earth is
the magma (iron and magnesium) that makes
up the mantle.
It is mostly solid except the outer 200-300
Km which is extremely hot and goopy; very
plastic-like.
This outermost liquid layer of the mantle is
referred to as the asthenosphere.
Earth's Interior
Zones within the earth
4. Mohorovicic Discontinuity: Boundary
between the mantle (asthenosphere)
and the Lithosphere (crust).
• The Moho serves to separate both oceanic
crust and continental crust from underlying
mantle.
The Mohorovicic Discontinuity, or "Moho", is the boundary between
the crust and the mantle. The red line in the drawing below shows its
location.
Earth's Interior
Zones within the earth
• 5. Lithosphere (crust): This is the top
layer of the earth, which is basically
hardened mantle (magma).
• It contains two segments,
– the oceanic crusts
– continental crusts.
– (diagram in book or online)
The oceanic and
continental crusts
– Note: this is the same crust, it just depends
how thick it is to determine if it is part of the
Oceanic or Continental Crust.
– For instance, if you drained all of the water
from earth, then there would be one, giant
Continental Crust.
– Likewise, if you flooded everything, you'd
have one, giant Oceanic Crust.
UNIT I: Land and Water Forms
• In this lesson you will:
• define the term topography (P. 6 and
glossary);
• differentiate among the terms hill and
mountain as well as plateau, and plain,
(P.7).
Topography
• The term referring to the surface features of
the earth like, hills, mountains, valleys,
plains, plateaus and other relief features.
• The book defines it as " the natural and
human features of the earth's surface".
– `The map that follows shows the topographical
features of South America.
Pittsburgh
Elevation & Relief
• Elevation
– The elevation of a geographic location is its
height above a fixed reference point, often the
mean sea level.
Marinia Trench: https://www.youtube.com/watch?v=r17kLJxJcwM
• Relief
– The difference between the highest and
lowest elevations in an area. A relief map
shows the topography of the area.
• Hills - are typically defined as areas of
upward relief less than 300 - 600M.
• Mountains - are defined as areas of
upward relief greater than 300- 600M.
• It is important to note that books differ on
the actual relief required for a hill to be a
mountain but the difference is one of the
degree of elevation.
• Plains - are areas of flat land with very
little relief. They are found at low
elevations often along coasts and in
the center of continents.
• Plateaus - are areas of flat land with
little relief. They occur at high
elevations and are associated with
mountains.
• Like hills and mountains plains and
plateaus differ based on elevation.
Land Form Patterns
• In this lesson you will:
• 1.1.11 Describe global patterns in the
location of landforms. (k) (P. 7 questions
4-7).
Where do the world's major
mountain ranges lie?
Can you identify the "Rockies in North America", the "Andes in
South America", and the "Himalayas in Asia" on the map?
Land Form Patterns
• Most mountains and high elevations are
located on coasts of continents.
• Large mountain ranges occur along the
west coast of North and South America.
Plate Tectonics
• In this lesson you will:
• 1.1.1 Explain how compressional forces
are caused. (k)
• 1.1.2 Explain how tensional forces are
caused. (k)
• 1.1.3 Relate selected plate movements
to compressional and tensional forces.
(a)
Plate Tectonics
• Tectonic plates move or float on top of the
asthenosphere .
• The plates are forced in specific directions by
the flow of magma beneath.
• The magma forms convectional currents. The
magma closer to the core heats and then rises
towards the surface as its density decreases.
• Once the rising magma reaches the lithosphere
it moves in opposite directions.
Compressional Forces
• Occur where two tectonic plates come
together.
• They compress against each other.
– Subduction Zones sometimes occur where
compressional forces result from two plates
colliding.
Tensional Forces
• Occur where two tectonic plates are pushed
apart.
• The tension is created as the plates move away
from each other.
– Ridge Zones sometimes occur where
two plates move apart. The magma
rises between the plates and forms a
ridge.
Volcanoes
• Volcanoes can occur at subduction zones or at
ridge zones.
• At subduction zones the compressional forces
sometimes leave a crack in the crust that allows
the magma to reach the surface.
• At ridge zones the plates are moving apart which
allows magma to reach the surface from the
asthenosphere.
– Because of the excessive number of active volcanoes
on the coast around the pacific ocean it is known as
the Pacific Ring of Fire.
The Development of the "Theory
of Continental Drift"
• Alfred Wegener was one of the first to
propose the theory of continental drift.
– While pondering the similarities between the
coastlines of South America and Africa.
– What if the continents were once all
connected and just drifted over the years?
Untold tragedies of Continental Drift. .
The Evidence
• Similar trees and Reptiles in many
different continents
• Glaciers that were then tropical forests
• Same types of rocks on continents close
to each other (yet separated by an ocean)
• The coastlines of Africa and South
America
The Flaw in Wegener's Theory
• He thought that each of the continents
were a separate plate--they were just
drifting on a never-changing ocean.
The Canadian Correction
• J. Tuzo Wilson was the 1960’s Canadian
scientist who started Wegner’s theory after
years.
– The plates of the earth are not composed of just land;
they're composed of ocean, too. In some cases, the
plates are just land, in others they're just ocean, and,
in still other cases, they consist of land and ocean.
They each have different boundaries and move in all
different directions.
Continental Drift
• It refers to the movement of the more than 20
plates (9 major) moving in different directions
• The continents drift at a rate of 2 inches a year,
or, as fast as a fingernail grows.
• It is believed to have started 200 million years
ago.
• The original single continent was named
Pangaea and the original ocean that surrounded
the land was called Panthalasa.
https://www.youtube.com/watch?v=UvIDxu7twpc
Plate Tectonics
Earthquakes
• Often occur at transform zones where the plates
are moving beside each other instead of toward
or away from each other.
• Notice that subduction zones occur where the
tectonic plates are moving towards each other
• While Ridge zones occur where the plates are
moving apart and transform zones occur where
plates are moving side by side.
Folded Mountains
• In this lesson you will:
• 1.1.4 Explain how compressional forces
create fold mountains. (k)
• 1.1.5 Differentiate between the terms
anticline and syncline.
How are fold mountains formed?
• Most Major Mountain ranges were formed
by folding.
• Fold mountains are formed when two
continental plates move towards each
other or a continental plate moves towards
an oceanic plate.
• The movement of the two plates forces
sedimentary rocks into a series of folds
• Fold mountains are usually formed from
sedimentary rocks and are usually found
along the edges of the continents.
• When plates collide, the accumulated
layers of rock crumple and form a series of
fold mountains.
• There are two types of fold mountains:
– young fold mountains ( 10 to 25 million years
of age, e.g. Rockies and Himalayas )
– old fold mountains (over 200 million years of
age, e.g. Urals and Appalachians of the USA)
Rocky
Mountains
Folding
• Folding is a process in which the Earth's
plates are pushed together in a roller
coaster like series of high points and low
points.
• Folding bends many layers of rocks
without breaking them.
• The peaks are known as anticlines
• The valleys are known as synclines.
Anticline fold
Syncline fold
Show 3 anticlines and two
synclines
Faults
• Faults are great cracks in the crust.
Types of Faults:
1. Normal Faults
2. Reverse Faults
3. Rift Valley
4. Fault Block Mountains
5. Overthrust Faults
Normal Fault
• A normal fault occurs when a plate on one
side drops down lower than the other side.
• Tensional Force
Reverse Fault
• A reverse fault occurs when one block is
pushed over the other.
• Compressional Force
Rift Valley
• A rift valley is where two normal faults
occur and the center drops.
• Tensional Force.
Block Mountain
• A block mountain is where two normal
faults occur and the center is pushed up.
• Tensional Force.
Over Thrust Fault
• An over fold is formed when one layer is
pushed over the other layer.
• This process occurs when the
compressional forces from one side are
greater than from the other side.
Volcanic Mountains
• Volcano is an opening in the earth's crust
through which magma, gasses, and ash
erupt.
• The shape of the volcano depends on the
thickness of lava.
• Most volcanoes occur on plate
boundaries.
Three Types of Volcanoes
• Ash and Cinder volcanoes
• Shield volcanoes
• Composite volcanoes
Ash and Cinder Volcanoes
• The simplest type of volcano.
• They are built from particles and blobs of
lava ejected from a single vent.
• As the gas are released, lava is blown
violently into the air.
• Most cinder cones have a bowl-shaped
crater at the summit and rarely rise more
than a thousand feet or so above their
surroundings.
• Cinder cones are numerous in western
North America as well as throughout other
volcanic terrains of the world.
• They are very explosive because the lava
is very thick and slow flowing. It blocks the
vent causing pressure to build up to high
levels before it finally blows.
Ash and Cinder Volcanoes
Shield Volcanoes
• Built almost entirely of thin fluid lava flows.
•
• Flow after flow pours out in all directions
from a central summit vent, or group of
vents, building a broad, gently sloping
cone of flat, domical shape, with a profile
much like that of a warrior's shield.
• They are built up slowly by the accretion of
thousands of highly fluid lava flows called
basalt lava that spread widely over great
distances, and then cool as thin, gently
dipping sheets.
• These are the least explosive because the
lava is so thin and fluid that it does not
block the vent and prevents pressure build
up.
Shield Volcanoes
Composite Volcanoes
• Type of volcano through which magma, from
reservoirs deep in the earth's crust, rises to the
surface.
• The lava varies causing it to be explosive one
time while the next time it can be gentle flowing.
Composite Volcanoes
Great web site
• http://www.nationalgeographic.com/forces
ofnature/