Principle Of Superposition

Principle Of Superposition Lesson 1 Assignment Unit I 1. In addition to various bits of information, there are 3 primary principles geologists use to place layers of rock according to age. The first, Principle of Superposition is the un-changed consecution of the rock, which contains the oldest stratum (a single sedimentary rock) located in the bottom of the rock. Superposition is the primary method to unveil the order of succession in which layers were formed in the rock. The second, Principle of Original Horizontally states that most strata is originally formed horizontally, which explains that steeply dipping strata was deformed at a much later date. This brings us to the third and last, Principle of Original Lateral Continuity. This is a stratum that patterned in all directions until the rock layers stopped at the ends of its original placement.

2. Catastrophism is a scientific method to explain extreme changes in geological structures in a short period of time. These catastrophism events may include earthquakes, severe flooding, volcanoes and extreme wind conditions. Uniformitarianism is the belief in slow evolution and slow change in geological Earth events. This states that Earth can only change over a long period of time.

Different parties, one believing in catastrophism and the other believing in uniformitarianism collided in the 19th century though being in close agreement at the same time. Under closer studies of the Paleozoic and Mesozoic era, these two theories posed problems for them, too short for uniformitarianism and too long for catastrophism. 3. By using the radioisoyope dating method, scientists are able to measure the age of a substance. This method is possible for measuring the invisible radiation emitted by phosphorescent substances. These atoms are called parents, and as it decays it will become a daughter.

By knowing the time it takes for an isotope to change from a parent to a daughter, we can measure the time without the interference of effects caused by catastrophism and uniformitarianism. To quickly explain the measuring process, you must take the # of parents and daughters mean in the rock and the percentage of parents remaining should be added to the measuring curve scale to find the amount of half-lives remaining. This will give you the age of the rock. 4. The planet Earth is estimated 4.6 billion years old.

Scientists were able to reach that number by using radioisotope dating. Using this method, scientists have measured from the Precambrian, Mesozoic all the way to the present. The process and details of radioisotope dating are explained above in 3. 5. a. Precambrian era, being the longest era consumed 4 billion of the 4.6 billion years of the Earth’s history.

Rocks during that age contained very little fossil history and were altered so much that it makes it difficult to know the conditions of that era. b. Paleozoic era began 570 m.y. ago and contained some of the earliest found life forms including the Trilobites, sharks, corals and the first life on continents including forests, insects and reptiles. The formation of the northern and southern Appalachians was also accomplished.

c. Mesozoic era extended from 245 m.y. to 65 m.y. This era was the death of the long survived trilobites but the beginning for dinosaurs and birds and the Andes. d. Cenozoic era extended from 65 m.y. to the present day.

This was the era of animals including horses, apes, humans and the formation of the Rocky Mountains, Alps and Himalayas. Unit II 6. The Earth’s rocks are divided into 3 different types. The first are igneous rocks, which are formed by volcanic magma coming to the surface and cooling. The second, sedimentary rocks are formed from the disposition or accumulation of sediments (mud, clay, sand, gravel and skeletal remains of plants and animals) from water, wind or ice.

There also is a second class of sedimentary rock that is formed a completely different way. Instead of mechanically depositing, it is chemically deposited forming limestones and evaporates. The third and last class, is the metamorphic rock. Metamorphic rocks are any rock that has been altered by being crushed, squeezed or heated. These rocks can be identified by their unique mineralogy and structure.

As a result of the changes, new types of rocks are formed. 7. Beginning with the granite, the most well known class of rock. These rocks have a speckled appearance with the light gray being its dominant color. Its chemical composition consists of high silica and low iron with magnesium content.

Unlike granites, the andesites are fine-grained and made up of an intermediate silica volcanic rock. This brings us to basalt, which are very dark colored rocks. Only looking at it very closely reveals the tiny grains of dark minerals the construct it. Unit III 8. Published in 1915, Alfred Wegener introduced Continental Drift Theory to the scientific world. This theory states the continents of the planet have moved and are still moving, and that the world once possessed only one huge continent (Pangea). Fellow scientists thought his idea was nuts, but at the same time it explained some unanswered questions involving the discovery of identical organisms found on separate continents separated by thousands of miles of ocean.

9. Comparing Wegener’s theory to the current theory of plate tectonics brings us to believe that he was not exactly correct but was on the right path. The Earth’s plates will overlap or push other plates giving them the ability to move very long distances. The new theory says that the plates moved and not just the continents. The plates may include the continents, the ocean floor or both. This concludes that continents can not move if the ocean floor doesn’t, they must move together. 10. Plate boundaries are broken up into 3 different groups: rifts, subductions and faults. Spreading oceanic ridges are located in all the major ocean basins of the world.

This will occur when 2 plates move apart from one another causing cracks to form. While this is happening the cracks will fill with molten lava and the new crust will expand the sea floor. These occurrences being indigenous to oceanic crust will constitute the largest mountain range on the planet. Subduction zones are the 2nd types of plate boundary. These are formed when plates come together and overlap.

If we compare subduction to spreading ridges, they differ greatly. Subduction will destroy the plates, where spreading ridges will constantly create new ones. Earthquakes traveling from depths of 370 miles will also effect subduction zones. Spreading ridges will only be altered by very shallow earthquakes originating only 44 miles deep. Two unique geological structures are formed from the Subduction of the ocean floor, trenches and andesitic volcanoes. This brings us to the third and last plate boundary, transform faults. Transform faults will run across continent’s ocean floor and combine with oceanic ridges, transforming fault pieces to create a long rectilinear zigzag.

While subduction zones are almost always arcuate in shape. The transform fault will simply be the connector between two differ …

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