Author Question: Describe the three basic rock types, how each are formed, and subcategories of each. What will be ... (Read 61 times)

jjjetplane · **on:** Jul 14, 2018

Describe the three basic rock types, how each are formed, and subcategories of each.

What will be an ideal response?

Question 2

Which part of Earth is primarily responsible for Earth's magnetic field? Why? What are the characteristics of magnetic reversals? How often do they occur? When will the next one occur, and what will happen when it does?

What will be an ideal response?

Amiracle · **Reply #1 on:** Jul 14, 2018

Answer to Question 1

Igneous: formed from solidifying and crystallizing of molten material. Two types, intrusive and extrusive.
Sedimentary: formed from the cementation of loose clasts. Types include clastic sedimentary, chemical sedimentary, and biochemical sedimentary.
Metamorphic: formed from the transformation of any igneous or sedimentary rock due to extreme heats and pressure. Two major types are contact metamorphism and regional metamorphism.

Answer to Question 2

Earth's magnetism is generated in the liquid outer core. Though the textbook doesn't discuss it, the answer to why is the dynamo theory. The locations of the north and south magnetic poles are surface expressions of Earth's magnetic field. This magnetic field migrates and, at various times in Earth's history, it has faded to zero and then returned to full strength with the polarity reversed. This has happened 9 times during the past 4 million years. The average period is about 500,000, but can range from 20,000 to 50 million years. The last reversal was 790,000 years ago. Based on magnetic decay, we are about 1,000 years from entering the next phase.