Earth Science

Earth science is the study of nature, distribution, behavior, and origin of the materials of the earth and its atmosphere. Earth science combines the sciences of geography, geology, geochemistry, geophysics, meteorology, and paleontology under a single course of study. It involves the application of principles from astronomy, biology, chemistry and physics.
The study of the earth science is called geology and scientists who study the earth are called geologists. This article deals with planet earth, as it is studied in geology. The study of the earth science includes mostly things of the earth. Therefore, the study of earth science is known as geology.

Rock formation takes place on a very large scale. Enormous masses of the earth’s crust and mantle move around, melt, and resolidify. These events also take place over a huge time scale. For example, the Himalayas – a young, still growing range of mountains- first began to form 15,000,000 years ago.
We find these enormous lengths of time almost impossible to comprehend. To help us describe such long periods of time, the earth history has been divided into eras. Each era is divided into periods. The recent period has been further divided into epochs. The different eras are:
Precambrian time: The Azoic, Archeozoic, and Proterozoic eras make up almost the first 4 billion year of the Earth’s earliest history. This length of time covers about 80% of the earth’s total history. It is often called Precambrian time. During the azoic era (4.5 billion year to 570 million year), the earth had it from begining. No evidences has been found in rocks era. Rocks of the Archeozoic era contain fossils of the first and most primitive life bacteria and tiny plants called algae.
The Paleozoic era: The Paleozoic era began 600000000 years ago and ended 240 million years ago. It included seven periods. These periods were from oldest to youngest: Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian and Permian. The Mississippian and Pennsylvanian

periods are sometimes considered a single unit called carboniferous period. The animal’s later Paleozoic periods include corals, sea urchins, and crayfish like animals called euryptids, shark, armored fish, lungfish, amphibians, and reptiles. Amphibians were the first air-breathing animals with backbones to walk on land.
The Mesozoic era: The Mesozoic era began 240 million years ago and ended 65 million year ago. It had three periods. These periods were, form oldest to youngest; Triassic, Jurassic, and Cretaceous. Fossil plants of the Mesozoic era include algae, ferns, mosses and conifers, all of which continued from the Paleozoic era. Single celled animals called protozoa lived in the warm seas of the Mesozoic era. There were many kinds of mollusk and fish, amphibians and reptile.
The Cenozoic era: The Cenozoic era began 65 million years ago and it is still going on. It covers the tertiary period which lasted until 1 and ¾ million years ago and the quaternary period which includes the present time. The tertiary period is divided into 5 epochs: Paleocene, Eocene, Oligocene, Miocene, and Pliocene. The Alps, Andes and Himalayan Mountains were formed during the Cenozoic era. A wide variety of plants and animals that we know today came into existence during the Cenozoic era. Small mammals that first appeared during Mesozoic era lived during roamed Europe and North America. By the Oligocene epoch, dogs and cats had appeared along with three-toed horse about as large as sheep. The earliest human fossils re in rocks of the Pleistocene epoch.