CHAPTER ONE UNDERSTANDING WHAT WE’RE STANDING OVER What is the nature of the ground beneath our feet In many ways the answer depends on where a person is standing The ground can be hard and rocky It might be covered by soft grasses In urban areas it may be covered by concrete But most people take the ground for granted We assume it is solidly underfoot supporting us our houses and our cities 4
Solid ground should not always be taken for granted It is capable of moving or changing shape These movements are usually very slow and cannot even be detected Other times as in the case of an earthquake the movement is sudden violent and catastrophic Earthquakes are dangerous destructive and sometimes deadly They are the result of powerful forces working inside the Earth that can cause the ground to move shake or even break apart 55
Humans have pondered the mysteries of Earth’s ground movements since the dawn of recorded history After all earthquakes have been rumbling and volcanoes have been erupting for longer than humans have been around to witness them So what makes the ground move or shake What makes a mountain explode with fiery fury Scientific understanding and theories concerning the forces that cause volcanic eruptions and earthquakes have grown immensely in the past 100 years 6
Geology and paleontology or the scientific study of the Earth’s rocks and the fossil remains of plants and animals have helped other scientists form theories about the nature of the ground and its movements The prevailing scientific theory of what makes the ground the continents even the floor of the ocean move or change shape is known as the theory of plate tectonics Fossil dig sites like Fossil Butte National Monument have helped scientists piece together theories on how similar fossils have been found in different continents and climates This can be seen as evidence of continental movement over time PLATE PERSPECTIVE Plate tectonics refers to geological plates or large rigid slabs of rock Tectonics comes from the Greek word meaning to build The term plate tectonics refers to the scientific study of how the Earth’s outer surface is constantly being built and rebuilt by a series of slowly moving plates 7
