Lecture 1 GLG 401

What are the four Eons of the Geologic timescale, in order from oldest to youngest? What

are the first 3 Eons referred to as? What is the most well-understood Eon?

What are the 3 Eras of the Phanerozoic Eon, in order from oldest to youngest?

What is the characteristic aspect of the Hadean Eon? [Answer: it lacks a rock record] What

marks the beginning of the Hadean? [Answer: formation of Earth] What marks the end of

the Hadean? [Answer: the oldest rock]

What is the age of the Earth, and how is that determined? [Answer: 4.54 Ga, from dating

meteorites]

How old is the oldest mineral on Earth? What kind of mineral is it? What eon is it from?

In what eon do geologists think there were multiple magma oceans?

What are two unique characteristics of the Archean Eon? [Answer: Evidence for permanent

solid crust (rocks) and evidence of water oceans]

The oldest rocks are from what Eon? [Answer: Archean]

Which Eon marks the first evidence of life? [Answer: Archean]

Potential Quiz Questions

Explain what stromatolites are. How old is the oldest stromatolite?

What are the unique characteristics of the Proterozoic Eon? [Answer: First evidence of

subduction (from subduction zone type rocks) and the earliest evidence for the rise of

atmospheric oxygen]

What are the 3 Eras of the Proterozoic, in order of oldest to youngest?

What is the Great Oxidation Event, and when did it occur?

What is a banded iron formation (BIF)? Make sure to explain what it is made of. Which

minerals make the darker layers, and which rock type makes up the reddish layers? Give the

logical reasoning behind the formation of BIFs. [Make sure to include the details shown on

the lecture slide]

How old are most banded iron formations (BIFs)?

What are the formulas for hematite and magnetite? Then, show that the formulas are

charge-balanced (i.e., have a total charge of 0). Remember that oxygen always has -2

charge.

What is chert? What is it made of? How is chert made in the oceans?