Download Utah History Ch. 2

Utah History Chapter 2 Utah’s Geological History Prehistoric Land and Animals According to geologists, for millions of years Utah land was covered by warm, shallow seas teaming with small shelled animals, fish and then reptiles. Dinosaurs lived here for millions of years. Then mammals, including giant mammoths and musk ox, came eventually, mountains and plateaus were formed. Volcanoes erupted, bringing copper, gold and silver from deep in the earth. People eventually came, living on what the ever­changing land provided. Do you ever stop to think about the shape of the land you live on? Does it have any mountains, hills, plateaus or valleys? Has Utah ever had floods or earthquakes? Will we ever have an earthquake again, and if so, how strong will it be? Geologists are scientists who study all these questions and more? They learn about the history of the earth by studying rocks and land formations. Geological Eras The earliest known era has been named the Precambrian Era. About 85% of all the earth’s 45 billion years falls within this era. The earth is divided into three eras: (3,825,000,000 years) 1) Paleozoic Era­ Means “ancient life.” This era produced the beginning of the fossil fuels we know as coal, oil and natural gas. 2) The Mesozoic Era­ means “middle life.” It is associated with dinosaurs. The Rocky Mountains were formed in this period. 3) The Cenozoic Era­ means “recent life.” Giant mammals replaced the dinosaurs. Large deposits of dinosaur bones have been found near the cities of Jensen, Vernal and Price. This place was cold. The Ice Ages. Many of the earth’s lakes, including the Great Lakes were formed. Utah’s Lake Bonneville was a remnant of the Ice Ages. Human beings lived here at the end of this period. Sediment, or loose sands, shells and pebbles, drifted to the bottom of the seas. Dinosaurs The worlds most complete dinosaur skeletons have been found in the Morrison Formation. Nearly 23 complete dinosaurs and 300 partial dinosaurs have been found in this digs or (quarries.) You can see the digs today at Dinosaur Quarry in Moab, or at Dinosaur National Monument near Vernal. Earl Douglas formed this Quarry. Utah’s State Fossil is the Allosaurus Shown on Page 29
Mountains Were Formed The Rocky Mountains were slowly lifted over thousands of years. How did this happen? North American plate forces North American continent into the Pacific plate on the west coast. This pressure forces mountains, peaks and cracks and faults. The earth’s surface was crunched together from faraway pressure of both the Pacific and the Atlantic Ocean floors. This pressure created great peaks and cliff. It also created faults or cracks in the surface. In Utah we have a fault line along the Wasatch Mountains. On page 31 is a picture of the Wasatch Fault. Volcanoes Made a Different Kind of Rock Igneous Rock came from deep inside the earth. Molten, or melted rock is constantly being formed. Sometimes this rock pushes through the earth’s crust as lava. For hundreds of years, Utah was covered by active volcanoes. Today all of Utah’s volcanoes are extinct to dead. Utah’s Rock and Mineral Resources Utah is rich in fossil fuels such as oil, natural gas, and coal. They were formed by the bodies of many, many plants and animals and much heat and pressure over millions of years. Utah also has a rich store of metals and minerals. Some of them were deposited by volcanic action. That is how the copper, gold, silver and molybdenum came to be in the Kennecott Utah Copper mine and in other places in Utah. What is the oldest rock found at Kennecott’s mine? Sandstone Utah has enough salt to satisfy the world’s needs for a thousand years. Utah’s geologic history has many building stones. Large beds of sandstone, limestone and quartz have been used for buildings. A type of marble is found near Fillmore. Two well­known uses of mountain granite are the Salt Lake Mormon Temple and the Utah State Capitol. The Ice Age The last major shaping of Utah took place in the Ice Ages. The Great Salt Lake is Utah’s largest body of water is located in the Great Basin which is a desert. Lake Bonneville Was Utah’s Ice Age Lake How deep was Lake Bonneville? At its largest, the lake covered an area of nearly 20,000 square miles and reached a depth of nearly 1,000 feet above the current Great Salt Lake. Ice Age Animals During the Ice Ages, now extinct huge mammoth, giant sloth, ancient bison, musk ox, cave bear roamed the earth. Page 36
Natural Forces Are Still Shaping the Land Today Utah earthquakes do cause limited damage from time to time. Utah has over 700 small earthquakes and about one large earthquake a year. Most are too small for us to feel. Earthquakes are a reminder that the earth is still changing. Read 33­39