9. upon what measurement is earth's latitude and longitude system based?
(1) star angles
(2) gravity intensity
(3) magnetism direction
(4) apparent solar diameter

Geologists know that potassium-40 decays to argon-40, with a half-life of 1.3 billion years. if an analysis of a feldspar crystal in a sample of granite shows that 75 percent of the potassium-40 atoms have decayed to form argon-40, what is the age of the granite

The european union was formally established in

What first caused people to consider that the continents were once one large landmass?