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 200-

300km 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.

-No one has ever seen the Moho. Drilling wells to that depth is very expensive and very difficult because of the extreme temperature and pressure conditions. The deepest well that has been drilled to date was located on the Kola Peninsula in the far north of Russia . It was drilled to a depth of about 12 kilometers. It is known as the Kola Superdeep Borehole which is located near the Norwegian border.

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

Rock Types

• Igneous - are crystalline solids which form directly from the cooling of magma. This is an exothermic process (it loses heat) and involves a phase change from the liquid to the solid state. The earth is made of igneous rock - at least at the surface where our planet is exposed to the coldness of space.

http://jersey.uoregon.edu/~mstrick/AskGeoMan/geoQuerry13.html

Rocks continued

• Sedimentary - In most places on the surface, the

igneous rocks which make up the majority of the

crust are covered by a thin veneer of loose

sediment, and the rock which is made as layers

of this debris get compacted and cemented

together. Sedimentary rocks are called

secondary, because they are often the result of

the accumulation of small pieces broken off of

pre-existing rocks. http://jersey.uoregon.edu/~mstrick/AskGeoMan/geoQuerry13.html

Rocks continued

• Metamorphic – are rocks that have been

created are transformed by great heat or

pressure. Their chemical composition is

altered as part of their meta (change)

morphis (form)

“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,

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 plates (which

has since been documented scientifically) 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.

cdli.ca

• 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. This layering system can result in cones as tall as 8,000 feet

above sea level.

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