Rock Cycle

Rock Cycle — page 1 — READING ROCKS In the late 1700s most scientists believed that planet Earth was very young no more than 6,000 years old They thought a great flood once shaped the land But one man thought differently James Hutton believed natural processes formed and continued to form the Earth over long periods of time He thought immense heat deep inside Earth pushed up the land to form new mountains 4 James Hutton 1726 1797

Rock Cycle — page 2 — Over millions of years weather eroded the layers of soft and hard rock of Monument Valley a desert region on the Arizona-Utah border Over time wind rain and other forces wore down the Earth Some of this mud and sand became new rock and the cycle started again According to Hutton this cycle of building up and breaking down over and over took much longer than 6,000 years Old as the Hills Jack Hills in Western Australia is home to the oldest pieces of Earth ever found Bits of the mineral zircon 4 4 billion years old were discovered among the rocks AUSTRALIA 5

Rock Cycle — page 3 — To prove his hypothesis Hutton and two other scientists traveled by boat down the coast of Scotland hunting for rocks to tell the story At Siccar Point on the North Sea the men found a unique formation At the bottom was gray layered rock like a layered birthday cake But the layers of this rock had been turned on their sides They stood straight up and down Siccar Point is now considered the most important geological location in the world 6

Rock Cycle — page 4 — To Hutton this proved that powerful forces had made the layers crash turn and shoot up out of the ocean where they had formed On top of the vertical rocks was another slab of gray rock and then another layer of newer red rock Since Hutton knew how long it took mud to build up in rivers he concluded Siccar Point must have taken hundreds of thousands of years to form Hutton published his findings in the 1780s Scientists of the day were slow to accept his ideas especially his suggestion that Earth was very old Today Hutton’s theories are the basis of the study of geology Many experts consider him the father of geology and the rock cycle Geological Time Rock layers called strata are used by scientists to determine the relative ages of events and objects in Earth’s history The Permian through Jurassic strata in the Colorado Plateau area of southeastern Utah show how scientists represent Earth’s geologic time vertically since new rock can only be laid upon older rock 7

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