Archean

Question 1

3 Reasons why there are no rocks older than 4.0 billion years old?

Answer 1

a.) many of the rocks have been metamorphosed
b.) deeply buried beneath younger rocks
c.) contain few fossils of any use in biostratigraphy

Question 2

5 Events during the Archean Eom

Answer 2

Differentiation of the Earth’s Layers
Formation of the Atmosphere
Formation of the Ocean
Formation of the Continents
Earth’s Earliest Organisms

Question 3

2 principal divisions of Earth’s surface

Answer 3

continents
ocean basins

Question 4

percent of Earth’s human population that lives on the continents

Answer 4

95%

Question 5

Earth’s first crust was probably?

Answer 5

Basalt

Question 6

Mineral that is 4.4 billion years old indicating that source rocks that old must have existed.

Answer 6

Zircons

Question 7

is not defined by its size, location, who discovered it, or whether it is surrounded by oceans. Rather, it is defined by the rocks it’s made of and how it came to be that matter.

Answer 7

Continent

Question 8

2 Major Features of the Continents

Answer 8

Stable Interiors
Mountain Belts

Question 9

extensive, flat stable areas that have been eroded nearly to sea level

Answer 9

Stable Interiors

Question 10

uplifted regions of deformed rocks

Answer 10

Mountain Belts

Question 11

expansive, flat regions composed of deformed crystalline rock

Answer 11

Shields

Question 12

Other flat areas of the stable interior in which highly deformed rocks, like those found in the shields, are covered by a relatively thin veneer of sedimentary rocks.

Answer 12

Stable Platforms

Question 13

the formation of large crustal provinces that, in turn, accreted with others to form even larger crustal blocks called?

Answer 13

Cratons

Question 14

The portion of a modern craton that is exposed at the surface.

Answer 14

Shield

Question 15

% of Earth’s exposed Precambrian crust is Archean

Answer 15

22

Question 17

2 most common variety of rocks in the Archean crust

Answer 17

greenstone
granite-gneiss complexes

Question 18

are actually composed of a variety of rocks, with granitic gneiss and granitic plutonic rocks being the most common, that were probably derived from plutons emplaced in volcanic island arcs.

Answer 18

Granite-gneiss complexes

Question 19

are subordinate, accounting for only 10% of Archean rocks, and yet they are important in unraveling some of the complexities of Archean tectonic events.

Answer 19

Greenstone belts

Question 20

Greenstone belts typically have what kind of structure?

Answer 20

synclinal structure

Question 21

The most interesting igneous rocks in greenstone belts

Answer 21

Komatiites

Question 22

Reason why komatiite can no longer be produced

Answer 22

ultramafic flows no longer occured

Question 23

theorized to be Earth’s first supercontinent, beginning its formation about 3.6 Ga (billion years ago), completing its formation by about 3.1 Ga and breaking up by 2.5 Ga.

Answer 23

Vaalbara

Question 24

supercontinent, existence of which is also only supposed, formed approximately three billion years ago.

Answer 24

Ur

Question 25

Areas of the supercontinent Ur are now parts of what continents?

Answer 25

Australia, Africa (Madagascar) and India

Question 26

believed to have formed during the Neoarchaean Era ~2.7 billion years ago (2.7 Ga) by the accretion of Neoarchaean cratons and the formation of new continental crust.

Answer 26

Kenorland

Question 27

Kenorland comprised what later became?

Answer 27

Laurentia

Question 28

Oldest evidence of life

Answer 28

Stromatolites

Question 29

Warrawoona Group age

Answer 29

3.3 to 3.5 billion years old

Question 30

supracrustal belt that dates to between 3.7 billion and 3.8 billion years old. Scientists have pored over the belt for signs of life, but until now found only indirect evidence.

Answer 30

Isua supracrustal belt