SATISH PRADHAN DNYANASADHANA COLLEGE,THANE Class- S.Y.Bsc Semister-IV Sub: Physics Paper-III Unit-I Topic- Geophysics Prof. Ms. Ankita P. Angre. Email: ankitaangre19@gmail.com

Geophysics

Internal structure of the Earth

Internal structure of the Earth Depth km Component layer Density g/cm2 0-60 Lithosphere -- 0-35 Crust 2.2-2.9 35-60 Upper mantle 3.4-4.4 35-2900 mantle 3.4-5.6 100-700 Asthenosphere - 2900-6378 Core 9.9-13.1

Meteorites

Meteorites Martian Stone Tagish Lake Willamette Iron Meteorites : A piece of rock or metals that has fallen to the earths surface from the outer space Meteorites are chunks of extraterrestrial material which impact on earth. They are important because they are sample of early solar system.

What do meteorites look like? Vesta Meteorite from Mars Allen Hills (Moon)

Stony-Iron Meteorites Meteorite Classification All Meteorites Undifferentiated Chondrites Differentiated Achondrites Iron Meteorites Stony-Iron Meteorites Chondrites are chemically primitive having compositions excluding volatile elements and very similar to the sun. The volatile carbonaceous chondrites are samples of slightly altered, ancient planetesimal material that condensed at moderate to low temperatures in the solar nebula.

Meteorite Classification Meteorite Classes Chondrites: relatively unaltered, formed as aggregates of primitive solar system material, unmelted asteroids, chondrules usually present, 86% of falls. Achondrites: processed by melting, formed from magma, crust or mantle of asteroid, no chondrules, 8% of falls. Iron meteorites: processed by melting, asteroidal core, 7% of falls. Stony-iron meteorites: processed by melting, core-mantle boundary of asteroid, 1% of falls.

The nonchondritic meteorites are differentiated materials of non solar composition that have undergone chemical processing like that which has affected all known terrestrial and lunar rocks.

Age of The Earth

The Earth is constantly changing planet The Earth is constantly changing planet. Its crust is continuously being created, modified, and destroyed. As a result rocks that records its earliest history have not bee found and probably no longer exist. We found evidence that the earth and other bodies of solar system are 4.5-4.6 billons year old.

Some Proof of age of the Earth 1 The oldest rocks found on the earth – Western Greenland – 3.7-3.8 billions years. The rocks found on the earth – Southern Africa – 3.4-3.8 billions years.

The oldest minerals – tiny zircon crystal found in sedimentary rocks in Australia 4.0-4.2 billions years old.

The oldest Moon rock are found on moon- 4.4-4.5 billions years old. 2 The oldest Moon rock are found on moon- 4.4-4.5 billions years old.

Majority Meteorites have ages 4.4-4.5 billion years old. 3 Majority Meteorites have ages 4.4-4.5 billion years old.

4 The best age of the earth is based on the time required for the time required for the lead isotopes in four very lead ores to have evolved from the composition of lead at the time of solar system. We found the age 4.54 billions years old.

Age of the Universe

1. The age of the universe can be estimated from the velocity and distance of the galaxy as the universe is expands. The estimates range from 7 to 20 billions years old.

2. The rate of evolutions of the star in globular cluster, which of the thought to be the oldest stars in the galaxy- 14-18 billions years old.

Technique to Determine Age of the Earth Radiometric Dating Annual Rock Layerings Incremental dating Cosmo genic Nuclide Geochronology Paleomagnetic Dating Magneto stratigraphy Luminescence dating

Radiometric Dating Radio activity was discovered by Henri Becquerel in 1896. The spontaneous breakdown or decay of atomic nuclei is termed radioactive decay that is the basis for all radiometric dating method. As a radioactive parent atom decay to stable daughter atom (e.g. Uranium decays to Lead), each disintegration results in one or more atom of the daughter than was initially present and one less atom of the parents. All rocks and minerals contain long lived radioactive elements that were incorporated into the earth.

Luminescence Dating Luminescence Dating technique observe ‘light’ emitted from material such as quartz, diamond etc. The luminescence technique utilized in geology are optically Stimulated luminescence(OSL) Cathodo luminescence(CL) Thermoluminescence (TL) Thermo luminescence are optically stimulated luminescence are used in archeology to date “fired “ object like cooking stones or pottery and can be used to observe sand migration.

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