Lecture 8

Question 1

Precambrian

Answer 1

• Archean and Proterozoic Eons comprise in interval of time informally called Precambrian, which spans 87% of the geologic time scale

Question 2

Hadean Eon

Answer 2

The oldest of the Precambrian eons; the time between Earth’s origin and the formation of the first rocks that have been preserved.

Question 3

Hadean Atmosphere

Answer 3

• Early Earth had a molten surface or thin, unstable crust
• Sustained by heat from abundant meteorites striking the
  Earth and the decay of radioactive elements
• Primitive atmosphere probably comprised of Hydrogen
  (H2) and Helium (He)
• Primitive gases lost to space early in Earth’s history
• Weak gravity prohibited retention of lighter gases
• Dispersed by strong solar winds

Question 4

Archean Eon

Answer 4

• Earliest organisms developed in an atmosphere lacking oxygen.
• The first oceans formed as
  rain from the skies

Question 5

Miller Experiment

Answer 5

An experiment that reproduced the conditions under which life began on Earth and amino acids and other organic compounds were manufactured.

First laboratory synthesis of amino acids

Question 6

Where did life originate?

Answer 6

Life probably began in the sea

Question 7

hyperthermophiles

Answer 7

Organisms that grow in extremely high temperatures (90 degrees C)

Question 8

chemosynthesis

Answer 8

Process by which some organisms, such as certain bacteria, use chemical energy to produce carbohydrates

Question 9

Stromatolites

Answer 9

Oldest known fossils formed from many layers of bacteria and sediment.

Question 10

Proterozoic Eon

Answer 10

• Early life like today’s earth.
• Almost half of earth’s history.
• 90% of Earth’s continental crust by the middle Proterozoic.
• Life forms evolved slowly
• First tine oxygen is used.

Question 11

Proterozoic Atmosphere

Answer 11

• More oxygen then Archean
• Current oxygen level is at 21%

Question 12

Snowball Earth - Late Proterozoic

Answer 12

Late Proterozoic, earth was mostly glaciers and snowy.

Question 13

Rodinia

Answer 13

A supercontinent older than Pangaea that formed about 1.1 billion years ago and began to break up about 750 million years ago.

Question 14

Grenville Orogeny

Answer 14

An episode of deformation that took place in the eastern United States and Canada during the Neoproterozoic.

Question 15

Pannotia

Answer 15

A supercontinent that existed during the Neoproterozoic. Was very short-lived.

Question 16

Banded Iron Formations (BIFs)

Answer 16

A sedimentary deposit that consists of alternating thin layers of iron oxides (such as magnetite or hematite) and iron-poor minerals (such as shale or chert). Jasper Knob in Michigan. Banded iron formations, which formed over a billion years ago, are often used today as a source of low-grade iron ore.

• It signals oxygen getting turned on (Input of oxygen)

Question 17

Is ultraviolet light harmful?

Answer 17

Yes