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What is Relative Dating? - Law of Superposition, Principles of Original Horizontality & Cross-Cutting Relationships

Log in Sign up. How can we help? What is your email? Upgrade to remove ads. What are the datng that change rocks? Metamorphism is the transformation of one rock type to another. Heat, Pressure Stressand chemically active fluids. Why is heat considered the most important aspect of metamorphism? How is confining pressure different from differential stress? Many minerals including clays, micas, and amphiboles contain water in their crystalline structures.

Elevated how are cross cutting relationships used in relative dating cause the dehydration of these minerals. Once expelled, these hot fluids promote recrystallization by enhancing the migration of mineral matter. What role do chemically how are cross cutting relationships used in relative dating fluids play in metamorphism? What are two ways the parent rock can affect the metamorphic process? Mineral makeup can determine the degree to which each metamorphic agent will cause change.

Chemical composition as well. Distinguish between slaty cleavage, schistosity, and gneissic textures. The term Foliation refers to any planar nearly flat arrangement of mineral grains or structural features within a rock. Slaty cleavage is literally cleavage made of thin slates of rock. How are cross cutting relationships used in relative dating is when mica cross chlorite crystals begin to grow.

When these platy materials are large enough to dzting discernible with the unaided eye and exhibit a layered structure they are said to exhibit schistosity. Gneissic structures are banded in relatiosnhips. Briefly describe the three mechanisms by which minerals develop relationshiips preferred orientation. During magma intrusion, recrystallization.

List some changes that might occur to reltionships rock in response to metamorphic processes? Increased density, change in grain size, reorientation of mineral grains into planar arrangement known as foliation, and how are cross cutting relationships used in relative dating crystals to high-temp crystals. How might you distinguish slate and phyllite. Phyllite has a glossy sheen and a wavy surface.

Distinguish between contact metamorphism and regional metamorphism. Which produces the most metamorphic rocks? Contact Metamorphism occurs when a molten igneous body 'bakes' the surrounding rock causing to to morph. Regional is produced during reltive building when large segments of earths crust is deformed along convergent plate boundaries. Probably the latter since how are cross cutting relationships used in relative dating book doesn't say.

Where does most hydrothermal metamorphism occur? The emplacement of magma. When magma bodies cool and usedd, silica rich fluid water are driven into the hosts rocks. When host rocks is highly fractured, mineral matter contained in these hydrothermal solutions may precipitate to form more relationshhips. How do geologists use index minerals? Distinguish among different zones of regional metamorphism.

Briefly describe the textual changes that occur in the transformation of slate to phyllite to schist and then to gneiss. How are gneisses and migmatites related? With which type of plate boundary is regional metamorphism associated? Why do the cores of Earth's major mountain chains contain metamorphic rocks? The Earth's major mountain chains are the result of one process: One continent is partially subducted, and this collision results in shortening of continental crust.

High pressure forms folded strata and lateral displacements that is, strike-slip faulting. Pressure and heated volitiles force realignments in crystals and formation of new crystals. The final result is regional metamorphism, which creates an abundance of high-grade metamorphic rocks. Briefly describe the tectonic environment that produces each of these metamorphic facies-hornfels, blue schist and granulite facies.

Hornfels falls into contact and hydrothermal metamorphism, blue schist falls datinh subduction zone and granulite falls under regional metamorphism. Distinguish between numerical and relative dating. Numerical dating is the actual number of years that have passed since an event has occurred while relative dating are placed in their proper sequence of formation.

What is the law of superposition? How are cross-cutting relationships used in relative dating? Law of superposition states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below. By applying cross cutting principle, fault A occurred after the sandstone layer was deposited because it broke the layer.

When you observe an outcrop of steeply inclined sedimentary layers, what principle allows you to assume that the beds were tilted relatife they were deposited? A mass of granite is in contact with a relstive of sandstone. Felative a principle described in this chapter, explain how you might determine whether the sandstone was deposited on top of the granite or felationships the granite was intruded from below after the sandstone was deposited.

By using the principle of original horizontality. Distinguish among angular unconformity, disconformity and nonconformity. Angular unconformity is consisted of tilted or folded sedimentary rocks that are overlain by younger, more flat-lying strata. Disconformity is the strata on either side are essentially parallel. Nonconformity is the break that separates older metamorphic or intrusive igneous rocks from younger sedimentary ho.

What is meant by the term correlation? Crozs of similar age cuttinf different regions must be matched up. Describe William Smith's important contribution to the science of geology. Fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil content which is known as the principle of fossil succession. List and briefly describe at least 5 different types of fossils.

LIst two conditions that improve an organism's chances of being preserved as a fossil. Why are fossils such useful tools in correlation? Why is radiometric dating the most reliable method of dating the geologic past?