Types of geophysical survey

There are many methods and types of instrumentation used in geophysical surveys. Technologies used for geophysical surveys include:

1. Seismic methods, such as reflection seismology, seismic refraction, and seismic tomography.

2. Seism electrical method

3. Geodesy and gravity techniques, including Gravimetry and Gravity gradiometry.

4. Magnetic techniques, including aeromagnetic surveys.

5. Electrical techniques, including electrical resistivity tomography, induced polarization and spontaneous potential.

6. Electromagnetic methods, such as magneto-telluric, ground penetrating radar and transient/time-domain electromagnetics.

7. Borehole geophysics, also called well logging.

8. Remote sensing techniques, including hyper spectral.

Lesson 3 Earth

Alternative names: Blue planet, Terra, Planet Earth

Physical characteristics

Mean radius	6,378.1 km (equatorial), 6,356.8 km (polar)
Surface area	510,072,000 km2
Volume	1.08321×1012 km3
Mass	5.9736×1024 kg
Mean density	5.515 g/cm3
Equatorial surface gravity	0.99732 g
Temperature	14˚C

A rough size comparison of Earth and the other three terrestrial planets: Mercury, Venus and Mars.

The Earth is the third planet from the Sun. It is one of the four terrestrial planets in our Solar System. This means most of its mass is solid. The other three are Mercury, Venus and Mars.

The Earth is home to millions of species of plants and animals, including humans. Earth is the only place in the universe where life has been confirmed to exist. Life is considered an important force in shaping the Earth. (For example, early life forms completely changed its atmosphere). Because of this, life is called a biosphere.

About 71% of Earth's surface is covered in salt water oceans. Earth is the only place in the universe where liquid water is known to exist at present.

The other 29% is made of rocky land in the shape of continents and islands. Earth interacts with other objects in the Solar System, particularly the Sun and the Moon. The Earth goes round the Sun roughly once every 365.25 days. One spin of the Earth is called a day and one orbit around the Sun is called a year. This is why there are 365 days in a year. Earth has only one moon, known as the Moon.

History The Earth and the other planets formed about 4.6 - 4.8 billion years ago. They were made of the leftover gas from the nebula that made the Sun. The Moon may have been formed after a collision between Earth and a smaller planet (sometimes called Theia). Scientists believe that parts of both planets broke off — becoming (by gravity) the Moon.

What it is made of Earth is a terrestrial planet. This means it is made up of solid rock unlike a gas giant such as Jupiter. It is the largest out of the four terrestrial planets in mass and diameter.

Chemical composition The Earth is composed mostly of:

iron	32.1%
oxygen	30.1%
silicon	15.1%
magnesium	13.9%
sulphur	2.9%
nickel	1.8%
calcium	1.5%
aluminium	1.4%
trace amounts of other elements	1.2

Shape The Earth's shape is an oblate spheroid. This means it is basically a sphere but it bulges around the middle. The highest point on Earth is the peak of Mount Everest at 8,848 m above sea level. The lowest natural point is the bottom of the Mariana Trench at 10,911 meters below sea level.

Memorize the words:

mean -- середній rough – грубий, приблизний terrestrial -- земний species – вид to confirm -- підтверджувати to exist – існувати to consider -- розглядати, вважати to interact – взаємодіяти spin – оберт leftover – залишок nebula – туманність oblate – сплющений біля полюсів to bulge – випинатися, виступати

Answer the questions:

1. What is the difference between equatorial and polar radii of the Earth?

2. What are terrestrial planets of the Solar System?

3. What is called biosphere?

4. How much of Earth’s surface is covered by salt water?

5. What is called a year and a day?

6. How old is the Earth?

7. What were the planets of the Solar System made of?

8. Name at least three main chemical elements of which Earth is composed.

9. What is the form of the Earth?