Please help me with numbers 1, 3 , 4 , 5 , 15 thank you . Skip 5 please Review Q

Question

Please help me with numbers 1, 3 , 4 , 5 , 15
thank you .
Skip 5 please

Review Questions IU terozoic eon ast catastrophism and uniformitarianism. How did 11. Why are fossils such useful tools in correlation? ents of each perceive the age of Earth? ish between numerical and relative dating hat is the law of superposition? How are cross-cuttin 2 Distinguish 12. In addition to being important aids in dating and corre- relationships used in relative dating? lating rocks, how else are fossils helpful in geologic investigations? you observe an outcrop of steeply inclined sedi 13. If a radioactive isotope of thorium (atomic number 90 mentary layers, what principle allows you to assume that the beds became tilted after they were deposited? mass number 232) emits 6 alpha particles and 4 beta par ticles during the course of radioactive decay, what are the atomic number and mass number of the stable daugh- ter product? 5 Refer to Figure 5 to answer the following questions a. Is fault A older or younger than the sandstone layer? b. Is dike A older or younger than the sandstone layer? 15. Assume that a hypothetical radioactive isotope has a hals 14. Why is radiometric dating the most reliable method of dating the geologic past? life of 10,000 years. If the ratio of radioactive parent to stable daughter product is 1:3, how old is the rock con- taining the radioactive material? What if the ratio were 1:15? fault A? d. Was the conglomerate deposited before or after fault B? e. Which fault is older, A or B? f. I 16. To make calculations easier, let us round the age of Earth to 5 billion years. a. What fraction of geologic time is represented by s dike A older or younger than the batholith? Amass of granite is in contact with a layer of sandstone lsin a nrinciple described in this chapter, explain how recorded history (assume 5,000 years for the length of recorded history)? b. The first abundant fossil evidence does not appear ning of the Cambrian period (approxi ha sandstone was de

Explanation / Answer

1. The theory of catastrophism believes that the changes in the earth's history have resulted from some short-lived, sudden, violent catastrophes or giant disasters that occurred for a short time period. These were the prevailing philosophy which guided peoples' explanations before the time of Hutton. On the contrary, the principle of uniformitarianism by Hutton believes in a much slower and gradual process that took place over long periods of time resulting in shaping the Earth. The principle states that "present is the key to the past" which means to understand the past, we must understand the present.

From the theory of catastrophism, the Earth was thought to be 6000years old but from the theory of uniformitarianism, the Earth was suspected to be much older than 6000years.

3. Law of superposition: This law is one of the fundamental principles of stratigraphy and was stated by Steno. It states that in any undisturbed sequence of sedimentary strata, the oldest layer is deposited at the bottom of the sequence followed by successively younger layer upwards. This implies that the younging direction is upwards.

Cross cutting relationships are important in relative dating because they help us to determine the relative ages of the features involved. The principle of cross cutting relationship states that any feature or strata that cross cuts another layer or strata is younger than the feature it cuts across. For example a dike which cuts through the layers of sedimentary rocks is younger than the layer of rocks which it cuts across.

4. The principle of horizontality. This principle states that under the action of gravity, the sediment layers are originally deposited in horizontal layers.

15. Given : half life = 10000 years.

This means after 10000 years the ratio of parent : daughter = 1:2

Given :

Ratio of parent to daughter = 1 : 3

If the ratio is 1:3 it means 2 half lives have passed.

1 half life = 10000 years.

2 half lives = 20,000 years.

Thus, required age of the rock = 20,000 years.

Again,

Ratio of parent to daughter = 1: 15

Ratio of 1:15 means 14 half lives have transpired.

Thus, required age of the radioactive material = 14 * 10000 = 1,40,000 years.

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