How Diamonds Form (Chapter 4, Key Terms & Key Concepts)

Question 1

Earth’s innermost layer

Answer 1

Core

Question 2

Ancient, large, and
stable parts of the earth’s
continental crust

Answer 2

Cratons

Question 3

The surface and outermost
layer of the earth.

Answer 3

Crust

Question 4

A geologic
process that delivers materials
(sometimes diamonds) to the
surface

Answer 4

Emplacement

Question 5

A category of
rocks formed from a molten state.

Answer 5

Igneous rock

Question 6

An igneous rock
that transports diamonds to the
surface.

Answer 6

Kimberlite

Question 7

An igneous rock, rarer
than kimberlite, that transports
diamonds to the surface.

Answer 7

Lamproite

Question 8

Layer between the
earth’s crust and its core.

Answer 8

Mantle

Question 9

A category of
rocks that have been altered by
heat and pressure.

Answer 9

Metamorphic rock

Question 10

A deep vertical formation at
the earth’s surface that results
from a kimberlite or lamproite
emplacement

Answer 10

Pipe

Question 11

Process in which two
crustal plates collide, forcing one
under the other

Answer 11

Subduction

Question 12

Diamond and graphite are both made
of carbon.

Answer 12

Key Concept

Question 13

Diamonds form in cratons, which are
located only under continental landmasses

Answer 13

Key Concept

Question 14

The carbon needed for diamond
formation is always present.

Answer 14

Key Concept

Question 15

Diamonds might wait hundreds of
millions of years before they’re carried
to the surface.

Answer 15

Key Concept

Question 16

Diamonds that exist today were
delivered to the surface between 2.5
billion and 20 million years ago.

Answer 16

Key Concept

Question 17

Kimberlites and lamproites transport
diamonds to the surface (through the pipe), but diamonds
don’t form in them.

Answer 17

Key Concept

Question 18

Very few kimberlites actually contain diamonds.

Answer 18

Key Concept

Question 19

During emplacement, if diamonds are exposed to high temperature along with decreased pressure for a long period, they will

Answer 19

convert to graphite.

Question 20

Diamond and graphite are both made of

Answer 20

carbon.

Question 21

How far beneath the earth’s surface do diamonds form?

Answer 21

90 to 140 miles (140 to 220 kilometers)

Question 22

The proper environment for diamond formation includes the right temperature, pressure and

Answer 22

the availability of carbon.

Question 23

Before arriving at the earth’s surface, diamonds might remain in the mantle for as long as a few

Answer 23

hundred million years.

Question 24

Diamond is hard and graphite is soft because of the difference in

Answer 24

the way their atoms fit together.

Question 25

Subduction occurs when

Answer 25

two of the earth’s crustal plates collide.

Question 26

Most of the world’s kimberlite pipes

Answer 26

do not contain diamonds in profitable quantities.

Question 27

The three main components of the earth are the crust, mantle, and

Answer 27

core.

Question 28

The deep vertical formations through which diamonds traveled to the surface are called

Answer 28

pipes.

Question 29

The first authenticated diamond discovered in South Africa is named the

Answer 29

Eureka.

Question 30

Scientists have found that diamonds form in two types of rocks, called

Answer 30

peridotite (igneous rock) and eclogite (metamorphic rock).

Question 31

The correct conditions for diamond formation exist under

Answer 31

cratons.

Question 32

The large, stable parts of the earth’s continental crust are called

Answer 32

cratons.

Question 33

Diamonds were delivered to the earth’s surface as recently as

Answer 33

20 million years ago