The Importance of Geologists G eology is the study of the physical features and history of Earth It is important because it helps us to do many things and it answers many questions we have How did Earth come to have its present shape and form What are the materials in the ground and how do they affect us How can we use them responsibly Scientists who answer these questions are called geologists A geologist in a laboratory takes notes as she looks closely at rock samples through a high-powered microscope 4
Geologists investigate a site near Lake Nyos Cameroon where deadly amounts of volcanic gas were released in 1986 Geologists help find important materials in Earth’s crust such as oil gas and minerals They also predict earthquakes and other natural hazards Geologists figure out where we can safely build things like houses office towers and power plants They also help us save important resources like water Other geologists study the makeup of what is underground including the remains of living creatures that lived long ago VOCAB U LARY Minerals are naturally occurring substances usually taken from the ground They make up Earth’s rocks sands and soils 5
The Geologist’s Laboratory M ost geologists agree that Earth is about 4 6 billion years old Earth’s surface has changed greatly since the planet’s beginnings After about 700 million years it developed a solid crust Geologists use the words geologic time to describe the vast amount of time that has passed since Earth started to form They divide this time into three broad periods called eons The Kasha-Katuwe Tent Rocks in New Mexico were formed by volcanic eruptions and by wind and water erosion into unique shapes that resemble tents or cones 6
Several layers of sedimentary rock are visible at Rainbow Basin a National Natural Landmark that is located near Barstow California THIN K ABO UT IT Think about a place you know well What changes might have occurred there over millions of years The two oldest eons are part of what is called Precambrian time The third eon which includes present time is called the Phanerozoic eon It is divided into three periods called eras the Paleozoic Mesozoic and Cenozoic eras Geologists learn about these different periods by studying the many layers of rock in Earth’s crust The deepest layers are the oldest More recent layers are closer to the surface Each layer contains unique types of rocks and fossils 7
