Big Idea 6: Earth Structures Description Over geologic time, internal and external sources of energy have continuously altered the features of Earth by means of both constructive and destructive forces. All life, including human civilization, is dependent on Earth's internal and external energy and material resources. Benchmark Number & Descriptor • SC.6.E.6.1 • Describe and give examples of ways in which Earth's surface is built up and torn down by physical and chemical weathering, erosion, and deposition. • SC.6.E.6.2 • Recognize that there are a variety of different landforms on Earth's surface such as coastlines, dunes, rivers, mountains, glaciers, deltas, and lakes and relate these landforms as they apply to Florida. WEATHERING • Weathering - processes at or near Earth’s surface that cause rocks and minerals to break down Salt weathering of sandstone near Qobustan, Azerbaijan. PHYSICAL WEATHERING • Process by which rocks are broken into smaller pieces by external conditions. • Types of physical weathering – Frost heaving and Frost wedging – Plant roots – Friction and impact – Burrowing of animals – Temperature changes CHEMICAL WEATHERING • The process that breaks rock through chemical changes • The agents of chemical weathering – – – – – Water Oxygen Carbon dioxide Living organisms Acid rain EXAMPLES of WEATHERING EXAMPLES of WEATHERING Ice causes weathering EROSION • Process by which weathered rock and soil (sediment) are moved from one place to another • Erosion gradually wears down the surface of the Earth. • Erosion carves the Earth's surface creating canyons, gorges, and even beaches. Types of Erosion • Wave action • Glaciers • Running water • Rock fall • Landslides • Mud flow • Avalanche • Wind TYPES of EROSION WIND EROSION • As wind blows, particles of sand/sediment blast large rocks. As a result, these particles cut and shape the rock. WATER • When water flows over land, erosion occurs. • When rain falls to the Earth, it can evaporate, sink into the ground, or flow over the land as runoff. • Runoff picks up pieces of rock and "runs" downhill cutting tiny grooves. TYPES of EROSION ICE • Glaciers wear down the landscape. • Pick up and carry debris that moves across the land along with the ice GRAVITY • Gravity pulls down mass. • How much erosion takes place is determined by the: • Sum • Slope • Speed • Surface Deposition • The process in which sediment is laid down in new locations – The end result of erosion Types of Deposition Water Deposition Wind Deposition • Alluvial fan- fan shaped deposit of sediment on land • Delta- sediment from a stream deposited where a river enters a large body of water • Sand dunes- large deposits of sand dropped from wind – Sand dunes can move as the wind picks up sand from the back of the dune and blows it to the front. Types of Deposition Glacial Deposition • As a glacier melts, it creates landforms by depositing the sediments it has been carrying. – Till-unsorted mixture of sediment containing fragments of various sizes – Moraine-mounds of sediment at the downhill end of the glacier and along its side • Long Island is a glacial moraine. KNOWLEDGE CHECK 1. What is the difference between weathering and erosion? 2. Describe 2 types of weathering. 3. Describe 2 types of erosion. 4. What is deposition, and when does it occur? KNOWLEDGE CHECK 1. 2. 3. 4. What is the difference between weathering and erosion? Weathering is the breaking apart of rocks and minerals; Erosion is the movement of the pieces caused by weathering. Describe 2 types of weathering. Physical – external conditions Chemical – chemical change Describe 2 types of erosion. Wind – blowing particles Ice – glaciers wearing down land What is deposition, and when does it occur? -The process in which sediment is laid down in new locations -The end result of erosion LANDFORMS of FLORIDA FLORIDA’S PAST • 240 million years ago: – Florida was connected to the Northwest section of Africa. • During Pangaea – Supercontinent • 200 million years ago: – Pangaea broke apart and the central Atlantic Ocean was formed. BUILDING FLORIDA The Florida Platform • Once the supercontinent broke apart, Florida sank under shallow water. • Many marine organisms thrived in this shallow water. • Most marine organisms were made of calcium carbonate. • Over time as these organisms die, the calcium carbonate turns into limestone. – Over time the layers of limestone have built up creating a solid platform for Florida. BUILDING FLORIDA EROSION OF Appalachian Mountains – About 30 million years ago, the Appalachian Mountains began to erode. – The sediments from these mountains were carried south by currents. – These sediments covered the limestone platform and began to build Florida’s ground. – Keep in mind, Florida is still underwater. BUILDING FLORIDA Ice Ages – During the Ice Ages, glaciers melted and refroze. – During this time, water levels rose and fell depositing sediments in various locations on the Florida peninsula. BUILDING FLORIDA An Arch of Islands – Key West is an arch of islands located south of the southern tip of Florida. – Corals grew under the shallow seas. As they died out, new corals grew, adding height to this land mass. – Eventually, the land surfaced creating the upper Keys. – The lower Keys were created by sand drifts which covered the coral and eventually rose to sea level. KNOWLEDGE CHECK 1. Describe three factors that helped form Florida. 2. How was the limestone platform of Florida formed? 3. How are coral and the Florida Keys related? KNOWLEDGE CHECK 1. Describe three factors that helped form Florida. Florida platform, erosion of Appalachian Mountains, and Ice Age 2. How was the limestone platform of Florida formed? These organisms die, the calcium carbonate turns into limestone. 3. How are coral and the Florida Keys related? Corals grew under the shallow seas. As they died out, new corals grew, adding height to this land mass. Eventually, the land surfaced creating the upper Keys.