Form 1 Science Chapter 9: Earth

CHAPTER 9: EARTH
9.1 THE SYSTEM AND STRUCTURES OF THE EARTH

The Earth system consists of four main components which are interconnected, namely atmosphere,
biosphere, hydrosphere and geosphere.

- Atmosphere
o Air zone covering the Earth’s surface

- Biosphere
o Life zone that consists of variety of life such as humans, animals, plants and
microorganisms

- Hydrosphere
o Water zone that includes rivers, lakes, seas and also water trapped as ice,
underground water and water vapour

- Geosphere

o Rock and soil zone on the Earth’s surface

ATMOSPHERIC STRATIFICATION

Earth’s atmospheric consists of five layers, each with its respective roles
- Exosphere layer ( 480km and above )

o Contains light gases such as helium and hydrogen
o Air becomes thinner towards space
o Communication satellites orbiting Earth in this layer allow phone calls and television

broadcasts
- Thermosphere layer ( 80 – 480km )

o Also know as the ionosphere because it contains ions that can reflect radio waves
o Aurora, a stream of colourful lights resulting from reactions of charged particles with

Earth’s magnetic field and atmosphere gases occurs here
- Mesosphere layer ( 50-80km )

o Burning and destruction meteorites occur in this layer
- Stratosphere layer ( 13-50km )

o This layer is suitable and stable for aircraft flights
o The ozone layer that contains ozone gas which absorb harmful ultraviolet rays from

sunlight is found here

o The ozone layer depletes when chlorofluorocarbons (CFCs) released from pesticides,
refrigerators and air-conditioners break down ozone molecules in the ozone layer

- Troposphere layer ( 0-13km )
o The layer where living organism breathes, wind blowing and where clouds, rain and
snow form


OCEAN STRATIFICATION

- Surface Zone
o The water is very shallow and light can penetrate
o Zone suitable as a habitat for plants

- Midnight Zone
o This zone has little or no light
o It is difficult for plants to live at this depth but this level of large marine animals,
such as giant squids and various species of whales

- Dark Zone
o This zone is very deep and no light can reach it
o Most animals in this zone have shimmering bodies or are able to glow in the dark

DISTRIBUTION OF WATER ON EARTH
The ocean contains a lot of water. Seawater is evaporated by sunlight and is taken to the mainland
by clouds before it falls back as rain water. The water in the rivers then flow into the ocean. The
water cycle process is continuous. It is said that the total amount of water contained in Earth, on
Earth’s surface and in Earth’s atmosphere is always constant.


















EARTH’S LAYERS
Earth can be divided into three main layers according to its physical properties, namely crust,
mantle and core. The mantel consists of the lithosphere, asthenosphere and mesosphere.
Lithosphere covers the crust and the top part of the mantel.


















EARTH IS THE ONLY HOME FOR LIVING ORGANISMS
Earth is the third planet from the Sun and is the only planet suitable for life in our Solar System. One
of the unique characteristics of Earth that make it suitable for all life is the Earth’s temperature,
which is not too hot or too cold compared to other planets. This is due to the Earth’s position, which
is not too near or too far from the Sun. The presence of water and oxygen on Earth also allows Earth
to host all life.

9.2 COMPOSITION OF THE EARTH
Earth’s crust is formed from various types of rocks, which differ in colour, structure, texture and the
way it is formed. The rocks can be categorised into three groups, namely igneous rock, sedimentary
rocks and metamorphic rocks. Each type of rock forms differently and takes thousands of years to
form. All rocks contain material known as minerals.

TYPES AND CHARACTERISTICS OF ROCKS



















THE PROCESS OF ROCK FORMATION

9.3 MAIN PROCESSES OF THE EARTH
Earth’s surface is formed by two processes, namely exogenic process and endogenic process.

Exogenic Process

- Process that occurs on Earth’s surface
- Example: Weathering, erosion, mass and land depletion, transport and sedimentation

o Weathering
§ It is a process of rock fragmentation and decomposition or decay due to
changes in temperature, rain water frosting and microorganisms

o Erosion
§ It is a process of eroding of the Earth’s surface by moving agents such as
water, wind and waves

o Mass and land depletion
§ They involve soil movement from the top of a slope to below as a result a
gravitational force

o Transport and sedimentation
§ Weathered or corroded materials are moved by agents such as running
water, wind, waves and glaciers
§ The materials will be sedimented when the velocity agents decrease


Endogenic Process

- Process that is caused by forces from within the Earth
- Forms and changes the Earth’s surface
- Example: Mantel convection process, magma activity and Earth’s crust movement (Planet

Tectonics)
o Mantel convection process
§ The high temperature in the mantel and the core of the Earth produces
convection currents in the asthenosphere layer
§ These currents are able to move Earth’s crust
o Magma activity
§ Volcano is a vent on the Earth’s crust that allows molten and hot magma to
flow out through it in a strong eruption
§ The erupted materials accumulate around the slope of the vent and from
volcanic cones
o Earth’s crust movement (Planet Tectonics)
§ According to theory of Plate Tectonics, the Earth’s crust is divided into
several pieces of plates
§ These plates constantly move resulting in collision and divergence which
produce various landforms on Earth and confidential drifts


9.4 GEOHAZARD PHENOMENA
The consequences of the endogenic process are occurrence of geohazards such as earthquake,
tsunami and volcanism.

Quicksand is a geohazard that usually occurs in wetlands while acid rain is a geohazard that usually
occurs in the industrial area.


SCIENCE AND TECHNOLOGY USED TO PREPARE FOR GEOHAZARDS
Advances in science and technology allow the invention of devices that could provide early warning
on occurrence of landslide and tsunami.

THE IMPACT OF GEOHAZARDS
Geohazards such as tsunami and earthquake can cause loss of life, diseases, starvation and damage
to properties. We should sympathise with and assist victims of environmental disasters.

9.5 AGE OF EARTH

wiggedThe age of Earth is estimated to be 4.5 billion years based on meteorites obtained. Earth has gone
through various stages of periods, which have change or shaped the Earth’s landscape. Geologists
define a long period of time as an era. Each era is divided into several periods


















.

FOSSIL
Fossils are Earth’s materials such as plants, animals and insects which have been submerged and
buried for a very long period of time.

9.6 EARTH’S RESOURCES AND APPLIED GEOLOGY
SURFACE WATER AND UNDERGROUND WATER

ECONOMIC MINERALS
Economic minerals in the Earth consists of metallic minerals, non-metallic minerals and rare earth
materials. Examples of metallic are iron ore, tin and gold while examples of non-metallic minerals
are coal and petroleum.

Rare earth minerals consists of on or more than on of 17 rare earth elements found inside
Earth’s crust. Even though almost all rare earth minerals can be found in abundance, it is however
not easy to separate them as they exist together with other rare earth elements. Because of the rare
minerals’ unique properties, they are very important in modern technology. They are used in
computers, DVDs, communication devices, television and other. Therefore, technology based on
rare earth minerals is very important to the development of the economy of the country and world
in general.

Petroleum and coal are used as fuel. How are they formed?

HYDROTHERMAL PROCESS
The water is heated naturally by the heat from the Earth. This is know as hydrothermal process.

























THE NEGATIVE EFFECTS OF UNPLANNED HUMAN ACTIVITIES
Human activities that are not well-planned may cause negative effects to all living things.