GEOPHYSICS
• This is the branch of physics that is concerning with the physical, chemical, geological, astronomical
and other characteristic properties of the earth.
❖ It deals with geological events such as the temperature distribution of the earth’s interior, the source, configuration and the geomagnetic field.
INTERIOR STRUCTURE OT THE EARTH
❖ The structure of the earth is composed of three major zones arranged in concentric manner. These
are;-
i. The crust
ii. The mantle
iii. The core
❖ Diagram below shows a cross-section of the earth’s interior region.
i. THE CRUST.
• This is the outer solid layer of the earth.
❖ It is extremely thin (5 to 15km) compared to the radius of the earth (6371km).
TYPES OF CRUST
i) Continental crust: Composed mainly with granites and sedimentary rocks.
ii) Oceanic crust: The denser oceanic crust floats at a lower elevation forming oceanic basins.
❖ The boundary between the crust and the mantle is called Mohorovicic discontinuity or simple
Moho.
ii. THE MANTLE
❖ Mantle lies between the crust and the core.
❖ It is made up of rocks both in solid and molten states and these rocks are said to be in a plastic
state.
❖ Circulation of materials in the mantle is the main mechanism of heat transfer from the core of the earth to the outer region of the earth. It is the main force that drives the movement of continents as well as volcanism and earthquakes.
❖ The boundary between the mantle and the core is called Gutenberg discontinuity.
iii. THE CORE
• This is the inner part of the earth. It extends from the Gutenberg discontinuity to the earth’s geometric centre.
❖ The core consists of two regions. Namely
i) The outer core: It is composed of a liquid of molten nickel and iron known as magma
ii) Inner core: It is composed of solid materials known as iron-nickel alloys. The material of inner
core is solid because of high pressure at this depth.
Question: Explain why the inner core of the earth is solid while the outer core is liquid even though
the temperature is high.
Answer: Because the inner core is composed of solid iron-nickel alloys and this solid metals exists
under high pressure. High pressure makes the material (inner core) to be in solid state.
TECTONIC PLATES
• This is the phenomenon in which the earth’s crust and part of the mantle are cracked into huge pieces.
❖ The movement of tectonic plates means that some continents are moving apart and some are
moving towards each other.
❖ This process is referred to as continental drift and has been going on for hundreds of millions year.
❖ Tectonic plate’s movements have split the continents as we know them today.
❖ The line where two tectonic plates meet is called a boundary.
TYPES OF BOUNDARY
a) Destructive boundary
b) Constructive boundary
c) Conservative boundary
a) DESTRUCTIVE BOUNDARY
• This is the one formed at the edge of two plates moving towards each other.
b) CONSTRUCTIVE BOUNDARY
• This is the one formed at the edge of two plates moving away from each other.
