HIN K LIK T E A S CIEN T IST WHAT IS OUT THERE CHAPTER 1 IN THE BEgINNINg Geology iS THe STudy of THe earTH’S rockS and shaped and developed over time and includes formations it involves how the land has been the things such as rocks that are composed of one or more minerals The ancient greeks wrote about minerals and started to classify them by their hardness not until the 1600s did people become more interested in geology though at that time a debate was raging among religious people over how to prove that the biblical great flood occurred With more people digging for clues and exploring the different layers of the earth it led to the discovery of fossils unlike any living crea tures The field of paleontology was born in the 1700s as people began studying prehistoric life The more people dug into the earth the more useful things they found Mining for energy sources and semi precious metals made people rich and also provided Fossils help scientists under stand ancient creatures such as the birdlike Oviraptor resources such as coal and oil during the 1800s national governments began 7
to fund geological surveys to map areas where both mineral and non-mineral resources were located By the 1900s scientists had developed radio metric dating This method allowed scientists to determine a fossil’s or mineral’s age by measur ing the amount of radioactive decay present Isotopes within an element are either stable such as what is found in nature or unstable Unstable isotopes give off energy in the form of radiation or radioactive decay Radioactivity is measured by units called curie named after Marie and Pierre Curie who discovered and worked with the element radium The curie mea sures how many atoms decay per second This technique could also date the age of the earth’s rocks based on the radioactive isotopes inside them The earth was estimated to be 4 6 billion years old In the 1960s Harry Hess from Princeton University came up with the theory of seafloor spreading which describes how the seafloor moves as it expands carrying the continents with it Hess’s advance ments in mapping the ocean’s floors allowed scientists to prove the existence of plate tectonics Earth’s outermost layer is composed of several tectonic plates floating on the next layer There are continen tal and oceanic plates The plates move between 0 4 and 6 3 inches 1 16 cm per year Where two plates meet is called a plate boundary Typically the plates either slide apart from or toward each other These actions create events such as earthquakes But they also cause geologic for mations such as mountains to develop Scientists estimate there are more than half a million earthquakes in the world every year Most of the earthquakes are not severe enough to be felt but about 100,000 IN THE BEGINNING While some scientists study fault lines opposite the famed Curies above researched radioactivity 9
