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Our earth is estimated to have originated, by whatever means, about 4,600,000,000 years ago and the eons since have been variously described and classified by geologists, paleontologists and archaeologists into eras and periods and epochs. Unfortunately each discipline has tended to use its own classification and at times this motley of terms has been quite confusing. On the next pages, tables have been constructed in an attempt at some clarification. In the story of man we are concerned only with the geological epochs labeled "Pleistocene" and "Holocene" of the Cenozoic, or recent era. The archaeological ages of man can be only roughly fit into the geological schema and we have attempted to present this relationship on the second of the charts.

The positions and relationships of land masses and seas have changed markedly throughout the time of the earth's existence. Some two hundred million years ago the Eurasian continent was separated from a combined land mass called "Gondwanaland" which consisted of the present South America, Antarctica, Australia and India, by a great ocean joining the Atlantic to the Indian Ocean and running through the area which is now the Mediterranean Basin. This great sea is called "Tethys" and it had a northern arm (Paratethys) which ran through the present Black, Caspian and Aral seas areas. The story of India's later collision with the Asian continent is in the section on Central and Northern Asia . Recent study of cores from the floors of the Mediterranean and Black seas has given clues as to the course of events there. When Africa collided with Eurasia, the Tethys was closed at Gibralter and the Near East area so that at first a large inland sea was produced, covering the Mediterranean Basin and much of Eastern Europe. Then, with severe climatic changes of six million years ago the Mediterranean area became dry, actually desert, for a million years, while the Black - Caspian - Aral regions became a stagnant, shallow but gigantic type of swamp. Then when the northern streams became re-activated the Paratethys drained into the Mediterranean Basin and both areas were converted to a network of fresh-water lakes at something like five and one-half million years ago. About 600,000 years ago, a great lake in the Carpathian Mountains silted up and the Danube spilled over into the Black Sea. As the last glaciers receded about 89000 B.C. the Mediterranean, which had apparently been slowly refilling as the Atlantic poured over Gibralter Straits, now broke over the Bosporus again to add salt water to the Black Sea. This gave rise to an anoxic stratum of stagnant, brackish water below the surface which remains to this day and precludes marine life in the lower levels. (Ref. 100 )

With reference to the charts on the next pages we should point out that they are in part inaccurate for the world as a whole. While bronze working was present all over the continent of Europe proper by 1,600 B.C. the northern half of Britain and all of Scandinavia as well as western Iberia and North Africa remained neolithic or chalcolithic. More remote parts of the globe undoubtedly still had an early Stone Age culture. The Hittites in Asia Minor had iron as early as 1,300 B.C. but it was worth forty times its weight in silver and its use spread very slowly from this center. The Assyrians brought the Iron Age to Egypt only in the 7th century B.C. and it was not used in central and southern Africa until one to three centuries after the birth of Christ. China had the Shang Bronze Age Culture about 1,600 B.C. but did not have iron works until the 6th century B.C.

Questions & Answers

Three charges q_{1}=+3\mu C, q_{2}=+6\mu C and q_{3}=+8\mu C are located at (2,0)m (0,0)m and (0,3) coordinates respectively. Find the magnitude and direction acted upon q_{2} by the two other charges.Draw the correct graphical illustration of the problem above showing the direction of all forces.
Kate Reply
To solve this problem, we need to first find the net force acting on charge q_{2}. The magnitude of the force exerted by q_{1} on q_{2} is given by F=\frac{kq_{1}q_{2}}{r^{2}} where k is the Coulomb constant, q_{1} and q_{2} are the charges of the particles, and r is the distance between them.
Muhammed
What is the direction and net electric force on q_{1}= 5µC located at (0,4)r due to charges q_{2}=7mu located at (0,0)m and q_{3}=3\mu C located at (4,0)m?
Kate Reply
what is the change in momentum of a body?
Eunice Reply
what is a capacitor?
Raymond Reply
Capacitor is a separation of opposite charges using an insulator of very small dimension between them. Capacitor is used for allowing an AC (alternating current) to pass while a DC (direct current) is blocked.
Gautam
A motor travelling at 72km/m on sighting a stop sign applying the breaks such that under constant deaccelerate in the meters of 50 metres what is the magnitude of the accelerate
Maria Reply
please solve
Sharon
8m/s²
Aishat
What is Thermodynamics
Muordit
velocity can be 72 km/h in question. 72 km/h=20 m/s, v^2=2.a.x , 20^2=2.a.50, a=4 m/s^2.
Mehmet
A boat travels due east at a speed of 40meter per seconds across a river flowing due south at 30meter per seconds. what is the resultant speed of the boat
Saheed Reply
50 m/s due south east
Someone
which has a higher temperature, 1cup of boiling water or 1teapot of boiling water which can transfer more heat 1cup of boiling water or 1 teapot of boiling water explain your . answer
Ramon Reply
I believe temperature being an intensive property does not change for any amount of boiling water whereas heat being an extensive property changes with amount/size of the system.
Someone
Scratch that
Someone
temperature for any amount of water to boil at ntp is 100⁰C (it is a state function and and intensive property) and it depends both will give same amount of heat because the surface available for heat transfer is greater in case of the kettle as well as the heat stored in it but if you talk.....
Someone
about the amount of heat stored in the system then in that case since the mass of water in the kettle is greater so more energy is required to raise the temperature b/c more molecules of water are present in the kettle
Someone
definitely of physics
Haryormhidey Reply
how many start and codon
Esrael Reply
what is field
Felix Reply
physics, biology and chemistry this is my Field
ALIYU
field is a region of space under the influence of some physical properties
Collete
what is ogarnic chemistry
WISDOM Reply
determine the slope giving that 3y+ 2x-14=0
WISDOM
Another formula for Acceleration
Belty Reply
a=v/t. a=f/m a
IHUMA
innocent
Adah
pratica A on solution of hydro chloric acid,B is a solution containing 0.5000 mole ofsodium chlorid per dm³,put A in the burret and titrate 20.00 or 25.00cm³ portion of B using melting orange as the indicator. record the deside of your burret tabulate the burret reading and calculate the average volume of acid used?
Nassze Reply
how do lnternal energy measures
Esrael
Two bodies attract each other electrically. Do they both have to be charged? Answer the same question if the bodies repel one another.
JALLAH Reply
No. According to Isac Newtons law. this two bodies maybe you and the wall beside you. Attracting depends on the mass och each body and distance between them.
Dlovan
Are you really asking if two bodies have to be charged to be influenced by Coulombs Law?
Robert
like charges repel while unlike charges atttact
Raymond
What is specific heat capacity
Destiny Reply
Specific heat capacity is a measure of the amount of energy required to raise the temperature of a substance by one degree Celsius (or Kelvin). It is measured in Joules per kilogram per degree Celsius (J/kg°C).
AI-Robot
specific heat capacity is the amount of energy needed to raise the temperature of a substance by one degree Celsius or kelvin
ROKEEB
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Source:  OpenStax, A comprehensive outline of world history. OpenStax CNX. Nov 30, 2009 Download for free at http://cnx.org/content/col10595/1.3
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