## Selasa, 26 Mei 2009

### THE FORMING OF SURFACE OF EARTH

At the end of the chapter, students should be able to :

1. Explain how landform are a result if internal forces of crustal movement

2. Describe how landform are modified by external forces

3. Discuss how landform affect people

THE FORMING OF SURFACE OF EARTH

A. Endogenic

its resulting features such as a rock that originated within the earth

Endogenic power consist of :

1. Tectonic

The movement of plates which make up the earth’s crust. We call the tectonic is movement plates. The movement is very slowly-between 1 – 5 centimetres per year- so we do not feel the movement.

( The mantle made of liquid rock that flows in certain directions due to convection currents. Movement of the mantle cause the crustel paltes that lie on to move )

Kind of tectonic or movement plates is :

a. Fault

Is a fracture in rock along which the adjacent rock surfaces are differentially displace

-or-

plates slide past each other along the cracks of the earth crust

As the plates move, they may

- Slide past

- Pull a part

- Push toward each other

“When plates move a part, the molten mantle beneath the earth’s crust will rise up to create new landform like volcanoes”

“When plates push towards each other, mountains and volcanoes may be formed”

Fault consist of :

1. Graben Fault is up displace
2. Horst Fault is down displace
3. Compiling Fault is two or more displace / fault compailing

b. Folding

When two plates collide with each other, some of the layers of rock which make up the earth’s crust buckle and form fold

or

a bend in rock strata or other planar structure, usually produced by deformation and recognized where layered rock have been distroyed into wavelike form

Demontrate with cardboard !!

(The amount of folding that takes place can be so small that is hardly noticeable, or it can be so large that mountain are formed as a result

these mountain are called fold mountain)

Example,

Fold mountain is Himalayas in Nepal.

Mount Everest are located in the Himalayas.

Himlayas were first formed around 40 – 50 million years ago and they are still growing today.

Why ?

Because the Himalayas are located along two plates (indoaustralian and Eurasian plates and that still pushing againt each other

2. Vulcanicity

Process magma pushes its way into crust of the earth and reaches the earth surface through cracks which are often found along boundaries of plate.

Lava is when magma reaches the earth’s surface

Eruption is process of outpouring the lava to earth’s surface

Volcano is process of magma escapes to the earth’s surface through a single hole and hardened lava built up from many eruptions results in a cone shaped mountain

“Volcanoes have the same basic structure but their shapes and sizes are possible reasons for different, Why ?

Because depend of

1. Rate of flow

2. Compotition of lava”

( Open Chapter of Volcanicity )