Transcript LANDFORMS

LANDFORMS
Patterns and Processes
Structure
• From the surface, the Earth is a planet of
continents and oceans.
• There is constant motion on the earth’s
surface.
• Seismology is the study of earthquakes.
Scientists use seismology to see into the
interior of the Earth.
Structure of Earth’s Interior and Surface
(pp. 4-9)
Structural Zones of the Earth
• Inner Core
- 2700 km
- Solid Fe with some Ni
- 4000 to 6000 °C
• Outer Core
- 2300km
- Molten Fe with some Ni
- over 4000 °C
Structural Zones cont.
• Mantle
- 2900 km
- Divided into lower and upper layers
- largely solid except for the upper 200300km of upper layer called the
ASTHENOSPHERE which is in a
plastic like state.
- Made mostly of magnesium and iron
silicates
Structural Zones cont.
• Mohorovicic Discontinuity
- The boundary between the mantle
and the lithosphere, at which earthquake
waves change speeds.
- Was discovered in 1909 by Andrija
Mohorovicic, a Yugoslavian seismologist.
Structural Zones cont.
• Lithosphere
- 1-100km
- made up of the lightest elements
and compounds
- can be divided into 2 layers, one
under ocean basins (sima) and
one making up the continents (sial)
- Rocks of continents are also called
the crust
“Rocks and Minerals”
• Rocks are formed by minerals mixing together
and solidifying due to physical or chemical
processes.
• Three categories of rocks: (see page 6)
1. Igneous
2. Sedimentary
3. Metamorphic
• Construct a table with these headings: rock
category, describe formation, possible
location.
Topography
• Topography refers to the physical / landform
features of the earths surface.
• Mt Everest is 8848 m above sea level. The
Marianas Trench is 11,034 below sea level.
Topography is all the features in between.
Topography
Pangaea "all the earth"
• In 1915, the German
geologist and
meteorologist Alfred
Wegener (1880-1930)
first proposed the
theory of continental
drift, which states that
parts of the Earth's
crust slowly drift atop a
liquid core.
• Wegener
hypothesized that
there was an
original, gigantic
supercontinent 200
million years ago,
which he named
Pangaea, meaning
"All-earth". Pangaea
was a
supercontinent
consisting of all of
Earth's land masses.
• Pangaea started to break up into two smaller
supercontinents, called Laurasia and
Gondwanaland
Plate Tectonics
• PLATE TECTONICS
The theory of plate tectonics (meaning "plate structure")
was developed in the 1960's. This theory explains the
movement of the Earth's and also explains the cause of
earthquakes, volcanoes, oceanic trenches, mountain
range formation, and many other geologic phenomenon.
• The plates are moving at a speed that has been
estimated at 1 to 10 cm per year. Most of the Earth's
seismic activity (volcanoes and earthquakes) occurs
at the plate boundaries as they interact.
The rocks of Gros Morne National Park and adjacent parts of western
Newfoundland are world-renowned for the light they shed on the
geological evolution of ancient mountain belts. The geology of the park
illustrates the concept of plate tectonics, one of the most important ideas
in modern science.
This is one of the main reasons why Gros Morne National Park has been
designated a World Heritage Site by UNESCO (the United Nations
Education, Scientific, and Cultural Organization).
Compressional Force
----> compressional <-----When plates move towards each other they
create compressional force which causes rock
layers to bend, warp, or be pushed upwards.
Compressional forces are forces that squeeze
crustal rock together.
Formation of the Himalaya
Mountains
http://www.ascensiongateway.com/blog/uploaded_images/himalayas-716479.JPG
Tensional Force
<------- tensional----------->
When plates break apart, moving away from
each other, they create tensional force.
Tensional forces are forces that pull crustal rocks
apart.
Sometimes these tensional forces are so
strong that an opening is created allowing the
magma or lava to force it’s way up through.
This lava cools and forms a ridge. These
zones are referred to as RIDGE ZONES
Crustal Movement
Fold Mountains
Fold Mountains
• Most Major Mountain ranges were formed by
folding.
• The collision of continental plates causes the
thin crust (lithosphere) to bend.
• For example the Appalachian mountains and
the atlas mountains were formed by folding
when North America and Africa collided 400
million years ago.
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• All rock that is put under extreme pressure for
long periods of time (thousands or millions of
years) will fold like clay.
• 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 Anticlines are folds in rocks that
bend upwards. Synclines are folds in rocks that bend
downwards. Joints are parallel cracks in rocks.
An anticline is a convex up fold in rock that
resembles an arch like structure with the rock
beds (or limbs) dipping way from the center
of the structure
A syncline is a fold where the rock layers
are warped downward. Both anticlines
and synclines are the result of
compressional stress.
Picture of Syncline fold in
Quebec
Mountains by Faulting
• Faults form in rocks when the stresses
overcome the internal strength of the rock
resulting in a fracture.
• A fault can be defined as the displacement of
once connected blocks of rock along a fault
plane. This can occur in any direction with the
blocks moving away from each other. Faults
occur from both tensional and compressional
forces.
Normal Faults occur when tensional forces act
in opposite directions and cause one slab of the
rock to be displaced up and the other slab
down.
Faults cont.
• A Rift Valley is a valley
bounded by two
roughly parallel faults
formed when the rocks
of its base moved down
the fault plane
• Block Mountains are a
mass of upland,
bounded by faults. The
surrounding rocks may
have sunk, the
mountain block may
have risen, or both may
have occurred
Reverse Faults develop when compressional
forces exist. Compression causes one block to
be pushed up and over the other block.
Overthrust Fault
is a fault that has previously undergone folding
with one set of rock layers pushed up and on
other rock layers
Mountains by Volcanoes
Ash and Cinder Cones
• A cinder cone is a volcanic cone built almost entirely of
loose volcanic fragments called cinders. They are built
from particles and blobs of congealed lava ejected from
a single vent.
• As the gas-charged lava is blown violently into the air, it
breaks into small fragments that solidify and fall as
cinders around the vent to form a circular or oval cone.
• Most cinder cones have a bowl-shaped crater at the
summit.
• Cinder cones rarely rise more than 300-500 m or so
above their surroundings, and, being unconsolidated,
tend to erode rapidly unless further eruptions occur.
• Cinder cones are numerous in western North
America as well as throughout other volcanic terrains
of the world.
Shield Cones
• Shield cones (shield volcanoes). Primarily a liquid
flow event. Basic lavas, having a lower viscosity,
are very fluid.
• Such flows cannot pile up to form steep slopes.
• They spread out, travel fast, and go far, eventually
cooling into thin, nearly horizontal sheets of rock.
• As successive layers are stacked up from
hundreds, if not thousands, of eruptions, a
gently sloping cone, or flattened domical
mountain develops, with its characteristic
caldera at the summit, and pit craters along
some of the rift zones--a shield volcano.
Internal structure of a
typical shield volcano
COMPOSITE CONES
• Composite cones are volcanic cones made
up of alternating layers of lava and rock
particles. Weak points may develop along the
sides of composite cones. Lava flows out of
these weak points to form smaller cones.
• Composite volcanoes represent some of the greatest and
most violent types of volcanoes on earth's surface. A
typically composite volcano is a steep sided, large structure
with a symmetrical cone. The cone is built from alternating
layers of lava flow, volcanic ash, cinders, blocks, and
bombs.
•
There are two routes lava can flow from a
composite volcano.
• The first is by breaking through the crater walls from
fissures on the sides of the cone.
• The lava then cools once it has filled the fissures and
acts as a dike. This cooling activity acts as a benefit to
the cone because it adds in its strength and stability.
• The other direction of flow is simply from the crater at
the opening of the volcano.
• The most distinctive characteristic of the composite volcano is
the conduit system.
The conduit system allows for a magma reservoir deep inside the
earth's crust.
The pressure and the volume of magma is allowed to build up
under the crust until it is released in a violent eruption. The
eruptions of ash, lava, and cinder are responsible for the
continuing growth of a volcano.
Composite Cone
Contruction