Exam 4: Geologic Time Concepts and Principles

Evaporites in the rock record commonly indicate a period of arid climate.

What theory proposes that the same processes seen today have operated throughout geologic time (i.e. the present is the key to the past)?

Obtaining an absolute age for most sedimentary rocks is difficult.

If sedimentary rocks are tilted steeply, they most likely have experienced an episode of deformation.

A rock sample containing an isotope with a half-life of 28 million years has an initial mass of 184 grams. How much daughter isotope is present after three half-lives?

A division on the geologic time scale represents ____.

The present geologic time scale is based on relative and numerical dating techniques.

The emission of an electron from the nucleus is called ____________________.

The sentence "The Paleozoic Era occurred before the Mesozoic Era" is an example of absolute dating.

Compare and contrast the attempts by James Ussher and Lord Kelvin to measure the age of Earth. Explain what they did and why it was or was not scientific.

Atoms of a particular element that have a different number of neutrons in their nuclei are called ____________________.

The most notable trace in the geologic record of human activities is likely to be a(n) ____.

Assigning a specific date to a rock, which is measured in years before present, is known as ____.

The principle of ____________________ states that rock layers extend out in all directions until they pinch out or terminate against the edge of a basin.

Atoms with an unequal number of protons and neutrons are called isotopes.

Lead-214 (Pb-214) that undergoes beta decay becomes ____.

Geologists prefer to use rocks from closed systems when they radiometrically date the rocks. What is a closed system, and why is it important for radiometric dating?

The time necessary for one-half of the original number of radioactive atoms of an element to decay to a stable daughter product is known as a(n) ____.

In the early 20th century, Pierre and Marie Curie discovered that radioactive decay produces heat.

Lord Kelvin calculated Earth was 20-400 million years old. Why was he wrong?