GEOL 102 mid term study (part 2)

lectures 3-4

The Period beginning about 541 million years ago is_____________.

Cambrian

We are living in the ________ Epoch.

Holocene

K-Ar dating commonly has low precision in rocks that experienced high temperature (e.g., >125ºC) because _______.

it involves a noble gas that can cause a leakage

Prof. Strauss, an archaeologist from the American Museum of Natural History, wants to date the handwriting in a book stored in a British library. He would most likely choose the ________ method.

^{14C dating}

Dating a stratigraphic unit that contains the earliest animal fossils commonly uses_________.

U-Pb dating of zircons from ash beds

Among the following, the oldest Eon in the Geological Time Table is ___________.

Archean

The age of the oldest zircon grains from a sandstone in Australia is about______________.

4.36 billion years

Atomic mass number of an element refers to __________.

protons + neutrons of the atom

The time span needed for 3/4 of the original parent atoms to decay to daughter products would be _____________.

2 half-lives

Diamond is compositionally identical to graphite, but it is much harder than graphite because __________.

the chemical bonds in diamonds are much stronger than those in graphite

From the ages and cross-cutting relationship in the following diagram, the age of Unit C can be roughly estimated as _________.

younger than 110 m. y. (million years)

If a mineral crystal originally contained 80 atoms of a common, radioactive isotope of uranium, after 3 half-lives, how many atoms of the original isotope would remain in the crystal?

10

A mafic magma gradually rises to the shallow crust and cools down. During the shallowing and cooling process, which of the following minerals would likely form at the last stage

muscovite and quartz

Among the following rocks, which one has the highest metamorphic grade?

schist

The two most abundant silicate minerals of Earth's crust are__________.

quartz and feldspar

A laminated or layered structure in metamorphic rocks produced by the parallel alignment of platy mineral grains is called ____________.

foliation

In a cooling magma, ultra-mafic and mafic minerals such as olivine and pyroxene crystallized first at high temperature, followed by intermediate and sialic minerals such as amphibole, biotite, muscovite, and then Quartz. In the following, which mineral would be most vulnerable to weathering when they are exposed in Earth's surface environments?

olivine

Which of the following elements is the most abundant in the Earth's crust?

oxygen

Rocks formed by the very slow cooling of magmas beneath Earth's surface would have________.

large mineral crystals

Marble is a metamorphic rock derived from _______________.

carbonate rocks (limestone and dolostone)