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It’s the Rocks Fault. Types of Rocks. Igneous - formed when molten rock cools. Sedimentary – formed by the “cementing together” of small grains of sediment. Metamorphic – rocks changed by the effect of heat and pressure. volcano. magma. Igneous Rocks.
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Types of Rocks • Igneous - formed when molten rock cools. • Sedimentary – formed by the “cementing together” of small grains of sediment. • Metamorphic – rocks changed by the effect of heat and pressure.
volcano magma Igneous Rocks • These are rocks formed by the cooling of molten rock (magma.) Magma cools and solidifies forming igneous rocks
Igneous Rocks • When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside. • Afterwards, they decay at a predictable rate. By measuring the quantity of unstable atoms left in a rock and comparing it to the quantity of stable daughter atoms in the rock, scientists can estimate the amount of time that has passed since that rock formed. • Absolute geologic dating and relative geologic dating are two methods by which scientists try to determine the age of geologic evidence. • Carbon-14 dating is an example of absolute dating, and the law of superposition is an example of relative dating.
Fragments washed to the sea Rocks are broken up by the action of weather sea Sedimentary rocks Getting older Sedimentary Rocks • Sedimentary Rocks are rocks formed when particles of sediment build up and are “cemented together” by the effect of pressure and minerals.
Sedimentary Rocks • Sedimentary rock makes up about 75% of the rocks on the Earth’s surface. • Sedimentary rocks form on the surface of the Earth, anywhere that sand, mud, or other types of sediment collect. • Sedimentary rock layers can be disturbed by igneous rock. This happens when molten rock forces it way up through the layers above it. This forms igneous rock sections within and across the sedimentary layers. • The sedimentary rock layers must be there first, therefore the igneous rock intrusions are younger than the layers it cuts through. Sometime the molten rock will force its way to the surface and erupt, creating a younger igneous layer at the surface. • With time, more sedimentary layers can form on top of the igneous rock. Igneous rock is always younger than rock layers it cuts through.
Pressure from surface rocks metamorphic rock forming here Magma heat Metamorphic Rocks • Metamorphic rocks are formed by the effect of heat and pressure on existing rocks. • This can greatly affect the hardness, texture or layer patterns of the rocks.
Ice Cores Cylinders of ice that are drilled out of glaciers and polar ice sheets that help scientists know more about past climates. When snow falls it carries with it the compounds that are in the air at the time. In areas where temperatures are rarely above freezing (ice sheets and glacial areas), this builds up layer upon layer of compacted snow which becomes ice. Within these ice layers there is a record of the atmosphere at the time that the snow creating the ice layers fell.
Faults • Faults are fractures in Earth's crust where rocks on either side of the crack have slid past each other. • There are three kinds of faults: strike-slip, normal and reverse faults. Each type is the outcome of different forces pushing or pulling on the crust, causing rocks to slide up, down or past each other.
Strike-Slip Faults (horizontal movement) • indicate rocks are sliding past each other, with little to no vertical movement. Both the San Andreas and Anatolian Faults are strike-slip.
Dip-Slip Faults (vertical movement) • Normal faults: create space. Two blocks of crust pull apart, extending the crust. • The Basin and Range Province in North America and the East African Rift Zone are two well-known regions where normal faults are spreading apart Earth's crust.
Dip-Slip Faults (vertical movement) • Reverse faults:also called thrust faults, squeeze the crust, pushing two blocks of crust on top of each other. • These faults are commonly found in mountain ranges such as the Himalayas and the Rocky Mountains.
Pangaea • Formed about 260 million years ago during the Permian Period. • Earth’s continents moved together to form a great landmass, or supercontinent. • This caused deserts to expand to the tropics and sheets of ice covered land closer to the South Pole. • Many organisms could not survive the new climates.
Pangaea • Pangea holds together for much of the Triassic period where hot, dry conditions dominate the center of Pangea. • Pangea broke apart during the Jurassic period as North America separated from Africa and South America.
