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a. Explain how the age of rocks can be determined by radioactivity. Give an
example.
>>The rate of radioactive decay that the age of rocks in number of years could be
determined through radiometric age dating. To explain, many rocks contain small
amounts of unstable isotopes and the daughter isotopes into which they decay.
The amounts of parent and daughter isotopes can be accurately measured; the ratio
can be used to determine how old the rock is.
For example: U-235 (uranium as the parent isotope) is found in most igneous
rocks. In a stable condition without being heated at high temperatures, both the U235 and Pb-207 (lead as its daughter isotope) remain in the rock. A geologist can
compare the proportion of U-235 atoms to Pb-207 produced from it and determine
the age of the rock. Over number of long years, the U-235 can be decayed when
its nucleus become unstable due to too much neutrons. Per laboratory
measurements, the numbers of U-235 atoms have shown that each of the atoms
has a 50:50 chance of decaying during about 704 million years which means
during 704 million years, half the U-235 atoms that existed at the beginning of
that time will decay to Pb-207. That gives the half life of U- 235. The ratio of the
U-235 and the Pb-207 will give an estimated age of the rock.
b. How can scientists determine the internal structure of the Earth, if the depth of
the deepest well is only a tiny fraction of the earth's diameter?
Internal structures of the earth are determined thorough the seismic waves caused
by earthquakes. A knowledge on how seismic waves travel through different
substances and by determining how long it takes for the waves to reflect back to a
certain location, can be used in determining what are the internal structures of the
Earth. This indirect measurement is through measuring seismic waves with the use
of seismograph. .
c. Impact cratering, volcanism, tectonics, and erosion are the four major
processes that affect planetary surfaces. Briefly explain any two.
Erosion is displacement of any solid particles such as rocks, sediments, soil, etc.
which is usually caused by currents from water, wind or snow which usually occur
on downward motion. This process is one of the common causes of changes of the
earth structure. With erosion, land elevations can flatten and flat areas can deepen
and the area where the eroded particles will also have some changes on the shape
and formation.
Volcanism plays a major rule in shaping the planetary surfaces. The materials
given off from its lava during the eruption greatly changes the surrounding
surfaces in terms of the general feature and the general characteristics of the
environment. Volcanism can also change the planet's atmosphere such as
observations of lightning which have been attributed to ongoing volcanic
eruptions.
d. If the ages of the Earth and Moon are nearly identical, as believed, why are
most rocks found on the Moon so much older than Earth rocks?
>>Soon after the moon is formed, it stopped being geologically active unlike the
Earth which remained active all throughout these long period of time undergoing
rock cycles. Sine the age of a rock is the time since the rock has solidified, then
definitely most rocks of the moon will be found so much older than the rocks on
the Earth.
e. What do observations of the Moon suggest about its origin?
>>Through observations, speculation had been formed that that the moon had
originated from the Earth as caused by broken debris upon an impact of a massive
object that collided on the planet. It is suggested that such impact has caused the
tilting of the earth's axis. Based on observation, the earth and the moon are
moving apart at a rate of an inch yearly so that gives an idea that the moon could
had been more closer to Earth each year long ago The similarity of the age of the
moon and the Earth based on the age of some rocks also support an idea that both
may had formed from the same nebula upon their formations.
f. Which is hotter, Mercury or Venus? Why?
>>Despite being nearly twice as far from the Sun, Venus surface is much hotter
than the Mercury as caused by its surface composition mostly of carbon dioxide
and several layers of thick clouds composed of sulfuric acid. Such dense
atmosphere produces a run-away greenhouse effect causes the tremendous raise of
its surface temperatures.
g. Venus and Earth are about the same size and mass, yet carbon dioxide is a
major constituent of the atmosphere of Venus, while oxygen is much more
abundant in the Earth's atmosphere. Explain why the atmospheres are so
different.
>>The differences in their atmospheres can be attributed to the differences in the
proximity to the sun, the composition of the planet when it was formed, and the
presence of gases in the early atmosphere and the different chemical reactions that
took place along the process.
Theory suggested that both the Earth and Venus have similar compositions
including the presence of similar water and gas in the atmosphere in the
beginning. But due to close proximity to the sun, Venus was unable to keep water
in its surfaces upon exposure to ultraviolet rays of the sun. The water composition
was dissociated where Hydrogen escaped while oxygen combined with the rocks.
Similar process took place on Earth but different chemical changes occurred due
to its ability to keep its water and Carbon emissions has been absorbed thus more
gases left accumulating the atmosphere is oxygen. While the Venus surface
continued to undergo atmospheric chemical reactions which caused greenhouse
effect drying up its entire water surface and enhanced volcanism which caused
accumulation of carbon dioxide and acidic gases in its atmosphere which
continued to accumulate that made its surface hotter even more that the surface
temperature of the Mercury.
h. Explain why there are two general families of planets, rocky terrestrial and
gaseous jovian.
>> The early formation of the solar system was the primary determinant of the
formation of the planet as rocky terrestrial or gaseous Jovian as mainly influenced by
the mass and distance of the planet from the sun. As what is being thought, all planets
are made up with hard core. There was something called as solar wind which strength
was dependent on its proximity to the sun. Those planets that had been formed
proximal to the sun experienced hard blow of the solar wind which pushed the lighter
gases away from the certain planets thus became rocky terrestrial. On the other hand,
those farther from the sun are affected by weak solar wind thus leaving the gases to
build up and stay around the planet during formation which made the planet more
massive with more ability in retaining light gases thus became gaseous jovian.
i. The first planets discovered since ancient times were Uranus and Neptune.
Compare how they were discovered.
>> In a real sense, the Uranus and Neptune thought to be sister planets were the first
planets discovered since ancient times. However, they were far too faint to be
recognized as planets by the ancients, although occasionally, their brightness was
more than enough to be barely discerned by the human eye. Uranus was discovered
and recognized as planets by chance later in 1781 by Sir William Herschel. After the
discovery of Uranus, astronomers became puzzled by the fact that the planet was not
in precisely the orbit they predicted. It became obvious that there must be another
planet out there gravitationally affecting Uranus and pulling it out of its predicted
orbit and that lead to the discovery of the Neptune as planet in the year 1846. .
j. What knowledge do comets and asteroids provide to studies of the origin of the
solar system?
>> Comets and asteroids are good sources of materials thought to have not undergone
significant changes from the formation of the Solar System. Comets and asteroids are
far different far the planets’ materials which had significantly changed due to the
effects of the tectonics, and other environmental and atmospheric effects. Thus, that
leaves the comets and asteroids to provide materials which probably could probably
give some leads on what materials combined that formed the planets and the solar
system.