Difficulties in dating the geologic time scale

bruingarrania   10.04.2017  


difficulties in dating the geologic time scale



difficulties in dating the geologic time scale

Geologic Time Chapter 9 difficulties in dating the geologic time scale Earth; Chapter 17 in GEOS Version. After reading, studying, and discussing the chapter, students should be able to: Numerical dates — which specify the actual number of years that have passed since an event occurred. Nicolaus Steno — 2. In an undeformed sequence of sedimentary rocks or layered igneous rocksthe oldest rocks are on the bottom.

Layers of sediment are generally deposited in a horizontal position 2. Rock layers that are flat have not been disturbed. Principle of cross-cutting relationships — a younger feature cuts through an older feature. An unconformity is a break in the rock record, a long period during which deposition ceased, erosion removed previously formed rocks, and then deposition resumed.

Nonconformity — older metamorphic or intrusive igneous rocks in contact with younger sedimentary strata. The remains of relatively recent organisms — teeth, bones, etc. Entire animals, flesh included 3. Molds and casts 5. Coprolites fossil dung d. Gastroliths polished stomach stones. William Smith lates—early s rockford fosgate p3001 hook up that sedimentary strata in widely separated areas could be identified and correlated by their distinctive fossil content.

Principle of fossil succession — fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil content. Variant of the same parent atom b. Different number difficulties in dating the geologic time scale neutrons c. Different mass number than the parent atom. Spontaneous breaking apart decay of atomic nuclei 2. Parent — an unstable radioactive isotope c.

Daughter products — isotopes resulting from the decay of a parent c. Half-life — the time for one-half of the radioactive nuclei in a sample to decay. The percentage of radioactive atoms that decay during one half-life is always the same: However, the actual number of atoms that decay continually decreases c.

Comparing the ratio of parent to daughter yields the age of the sample. Two isotopes of uranium d. A closed system is required b. To avoid problems, one safeguard is to use only fresh, unweathered material. Half-life of only years 2. Used to date very recent events 3. Carbon is produced in the upper atmosphere. Useful tool for difficulties in dating the geologic time scale, archeologists, and geologists who study recent Earth history. Radiometric dating is a complex procedure that requires precise measurement 2.

Rocks from several localities have been dated at more than 3 billion years 3. Confirms the idea that geologic time is immense. Hadean — the oldest eon. Collectively, the Hadean, Archean, and Proterozoic eons are often referred to as the Precambrian. Not divided into smaller time units because the events of Precambrian history are not known in great enough detail. Precambrian rocks have been subjected to a great many changes. The grains composing detrital sedimentary rocks are not the same age as the rock in which they occur b.

The age of a particular mineral in a metamorphic rock may not necessarily represent the time when the rock formed. Geologic Time Chapter 9 in Earth; Chapter 17 in GEOS Version Learning Objectives After reading, studying, and discussing the chapter, students should be able to: Explain the difference between relative and absolute dating of earth materials. Discuss the Principle of Original Horizontality and how it relates to the Law of Superposition.

Briefly explain other principles used in relative age dating. List difficulties in dating the geologic time scale briefly explain dating party tokyo three types of unconformities. Briefly discuss fossilization, including the origin and types of fossils.

Discuss the correlation of rock layers using physical criteria and fossils. Briefly explain radioactivity and how it relates to absolute age dating. Discuss the procedure of radiometric dating and explain how it is used to obtain absolute ages. List the isotopes commonly used in the radiometric dating difficulties in dating the geologic time scale earth materials.

List and briefly discuss the major subdivisions of the geologic time scale. Briefly explain the significance of the Precambrian division of the geologic time scale. Two types of dates are used in determining geological ages A. Relative dates — placing rocks and events in their proper sequence of formation B. Numerical dates — which specify the actual number of years that have passed since an event occurred II. Principles and rules of relative dating A. Law of superposition 1. In an undeformed sequence of sedimentary rocks or layered igneous rocksthe oldest rocks are on the bottom B.

Principle of original horizontality 1. Rock layers that are flat have not been disturbed C. Principle of cross-cutting relationships — a younger feature cuts through an older feature D. One rock unit is enclosed within another Rock containing the inclusions is younger II. An unconformity is a break in the rock record, a long period during which deposition ceased, erosion removed previously formed rocks, and then deposition resumed 1. Types of unconformities a. Angular unconformity — tilted rocks are overlain by flat-lying rocks b.

Disconformity — strata on either side are difficulties in dating the geologic time scale c. Nonconformity — older metamorphic or intrusive igneous rocks in contact with younger sedimentary strata III. Fossil — the remains or traces of prehistoric life B. Types of fossils 1. Gastroliths polished stomach stones C. Conditions favoring preservation 1. Possession of hard parts IV. Correlation of rock layers A.

Matching rocks of similar age in different regions often relies upon fossils 1. William Smith lates—early s noted that sedimentary strata in widely separated areas could be identified and correlated by their distinctive fossil content 2. Principle of fossil succession — fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil content V. Dating with radioactivity A. Reviewing basic atomic structure 1.


difficulties in dating the geologic time scale

GEO 201 Geologic Time - Relative Age Dating


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