Getting a Handle on Time C1.4

Forces of Catastrophe During the 18th and 19th centuries geologists considered violent events such as earthquakes, volcanoes, floods, etc to be the main mechanisms of past change. William Smith proposed that he sedimentary rock layers he mapped were deposited over England by a series of floods. These violent explanations are now called catastrophist theories. A main component of these theories is that they involve processes of a different type or intensity that than those observed in the present.

How Much Time? These early theories of catastrophism fit in well with human experience. The processes at work in the present seem too weak and slow to explain evidence of a dramatic change in Earth’s past. It’s hard to imagine that the slow processes observed in the present could have resulted in the badlands, Mount Rundle, or Red Rock Coulee.

Complex Histories James Hutton believed that to unlock the mysteries of the past, you must understand the processes at work in the present. This was is the principle of uniformitarianism The principle that the geological processes in action today have always fundamentally operated in the same way throughout Earth’s history. Hutton observed nearly vertical layers of rock beneath horizontal layers. This lead him to first propose that the bottom layers were originally deposited horizontally but were subsequently tilted. Then, after a long period of erosion, many layers were deposited horizontally on top. This is called an unconformity A surface in a rock sequence that represents a break in the pattern due to erosion or a lack of deposition

What are Minerals & Rocks? Minerals: A mineral is a pure natural substance (element or compound) Rocks:is a natural substance that contains one or more minerals held together. The 3 types of rocks that cycle are: Igneous Sedimentary Metamorphic

What Are Igneous Rocks? Igneous rocks are formed when magma from Earth's core rises, cools, and solidifies forming crystals (called crystallization). Magma that moves out of the crust and cools quickly is called extrusive igneous rock (pumice). These igneous rock have small crystals. Magma that never reaches the surface and cools slowly is called intrusive igneous rock (obsidian). These igneous rock have large crystals.

What Are Sedimentary Rocks Sedimentary rocks are made up of sediments eroded or weathered from igneous, metamorphic, other sedimentary rocks, and even the remains of dead plants and animals. These materials are deposited in layers, or strata, and then are squeezed and compressed into rock (called lithification). Most fossils are found in sedimentary rocks.

What Are Metamorphic Rocks? Metamorphic rocks are produced when sedimentary or igneous rocks are transformed by heat and/or pressure. The word "metamorphic" comes from the Greek language, which means "to change form."

What is The Rock Cycle? The rock cycle below shows the life cycle of the three rocks and how they are related to each other.

Rock Cycle Activity

Assignment Nothing to Add to Your Timeline Practice Problems 1.4 Questions Pg. 318 #1-9