are Earth’s oldest known volcanic

rocks and contain three times as much

Line
magnesium as do most volcanic rocks.

(5)
This chemical composition suggests

that komatiites formed from the hottest

lava known ever to have erupted:
a

high concentration of magnesium

changes the physical properties of

(10)
lava so that unusually high tempera-

tures would be required for the lava

to exist as a liquid.

Komatiites’ discovery was surpris-

ing in light of then-current geological

(15)
theories about magmas, molten rock

that forms in the Earth’s mantle (the

layer beneath the crust) and composes

volcanic lava eruptions.
Prior to 1960,

geologists Bowen and Hess disagreed

(20)
over whether or not the very high tem-

peratures needed to produce magmas

rich in magnesium could have existed

on Earth.
Hess suggested that the

presence of water, probably released

(25)
from minerals decomposing in the

Earth’s mantle, might have meant that

a high-magnesium magma could have

existed at a lower temperature.
But

Bowen showed experimentally that the

(30)
high temperatures were indeed nec-

essary.
By 1960, it was generally

accepted that volcanic rocks with such

high levels of magnesium could not

exist, and thus the discovery of koma-

(35)
                    
tiites changed geologists’ assumptions

about the characteristics of the Earth’s

mantle around the time of the formation

of komatiites, between 2.5 and 4 billion

years ago.

--------------------------------------------------------------------------------

Q11:

Which of the following most accurately describes the organization of the passage?

A   Two divergent views of a scientific phenomenon are reconciled.

B    A phenomenon is described and its scientific significance is discussed.

C    The discovery of a scientific phenomenon is traced and its implications for further research are suggested.

D    A long-standing scientific theory is examined and recently discovered evidence is shown to support it.

--------------------------------------------------------------------------------

Q12:

Information in the passage suggests which of the following concerning the Earth’s mantle 2.5 to 4 billion years ago?

A    It contained magmas that were more significantly affected by the decomposition of minerals than are current-day magmas.

B    It contained a lower proportion of water that it contains today.

C    Its characteristics were accurately described by both Bowen and Hess.

D    Its temperature was sufficiently high to produce magmas with high magnesium content.

答案选的d，我选了a，请问在那里定位是d呢

Bowen showed experimentally that the

(30)
high temperatures were indeed nec-

essary.
By 1960, it was generally

accepted that volcanic rocks with such

high levels of magnesium could not

exist, and thus the discovery of koma-

(35)
                        
tiites changed geologists’ assumptions

就是说之前观点说不用高温,现在K的发现说明高温也可以.