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Frequently Asked Questions (FAQs)
Q1. What is geological time scale?
Ans. Geological time scale (G.T.S) is a time scale which
shows the total time span since the origin of earth to the
present day. It has been divided into several durations and
placed chronologically in geological time table in which each
duration includes its specific events. A geologic time scale
is composed of standard stratigraphic divisions based on
rock sequences and is calibrated in years. The longest time
period geologists use is called an Eon. Eons are divided into
shorter time periods called Eras, and Eras are divided into
even shorter time intervals called Periods. There are even
shorter periods of time called Epochs and Ages.
Q2. What are the radiometric methods?
Ans. Radiometric dating is based on the fact that the radioactive
isotopes of certain element decay at a constant rate and are
converted into other stable element. By calculating the rate
of disintegration and ammount the ammount of product
formed since the rock crystalized(formed), it is posssible
to calculate the date of rock formation.
Q3. Justify the statement that earth preserves its history in it’s
strata.
Ans. The Earth carries the history of geological events in
its rock layers. Steno argued that rock layers (or strata)
are laid down in succession, and that each represents
a “slice” of time. It follows that the oldest layers are at
the bottom and the youngest are at the top. With this
understanding geologists are able to determine the age
of rocks relative to one another. By assembling all these
layers together, scientists have worked out what is known
as the stratigraphic column or record of the various ages of
rock. This record spans the 4.6 billion year record of Earth’s
history. It shows record of organisms which lived on earth
and the climate of earth in respective periods
Q4. How is the age of different earth strata determined?
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Ans. Determining the age of rocks is critical to reconstructing
Earth’s history. Geologists rely on two basic types of
dating: absolute dating and relative dating. Absolute
dating establishes how many years ago a given event took
place. The most important methods of absolute dating
are based on the decay of naturally occurring radioactive
elements. Relative dating places historical events in their
correct order, but does not yield numerical estimates of
how many years ago the events happened. It may seem
odd that the two procedures are kept distinct—if scientists
can determine the numerical ages of rocks and fossils,
they should be able to put the evidence of ancient life in
the correct historical order. The problem is that only some
types of rocks and fossils can be numerically dated, so all
other evidence of ancient life must be related to age-dated
material by the techniques of relative dating.
Q5. Permian period witnessed a catastrophe of big dimensions
for the living organism, explian.
Ans. The Permian extinction—the worst extinction event in
the planet’s history—is estimated to have wiped out more
than 90 percent of all marine species and 70 percent of
land animals.Various theories seek to explain this mass
extinction. Some scientists think a series of volcanic
eruptions pumped so much debris into the atmosphere
that the sun was blocked out, causing a significant drop in
temperature and preventing plant photosynthesis, which
in turn caused food chains to collapse.
Q.6 “During Cretaceous period Nature invented the flower, and
the flowers bloomed for the first time” comment on the statement.
Ans. During the Cretaceous period Nature invented the flower,
and the flowers bloomed for the first time. Flower parts and
support for the sexual reproduction has been reported in this
time. This period also witnessed typical angiosperm pollen, insect
pollinated flowers, carpels, stamens and other floral organs.
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Q7. Give the organismal charateristics of the Jurasic period
Ans. This period is the period of cycads, conifers, and dinosaurs.
Due to the abundance of gymnosperms, this period is called
period of gymnosperms. Majority of the plant groups, such as
ferns, cycads, ginkgophytes and conifers reached their maximum
abundance. Williamsonia plant resembled a small tree with
diamond-patterned bark and palmlike leaves. First angiosperms
also arose during this period, toothed birds and marsupials also
flourished during this period.
Q8. Write an essay on the Palaeozoic era.
Ans. Palaeozoic era began 570 my ago and ended 225 my
ago. The fossil life of this era is well preserved. It has
been divided into six periods and each period has been
named after a place or region where the formations were
first discovered.
The periods of Palaeozoic era are as follows:
i)
Cambrian (570-500my) named for Cambrian the
Roman name for wales.
ii) Ordovician (from 500 to 435 my) named after a
tribal group of North Wales.
iii) Silurian (From 435- 395 my) named for Silures, an
ancient tribe of Britain.
iv) Devonian (from 395-345my) named for Devonshire
a place in England.
v) Carboniferious from 345-280 my named for
abundant coal bearing rocks it is divided further
into Missippian and Pennsylvanian periods
vi) Permian (from 280-225 my) named after an ancient
kingdom in Russia.
Life of Palaeozoic era: Abundance of algae resulted in the
increase of oxygen. This inturn resulted in ozone formation
and made life possible on land. All this paved way for land
invasion of plants during early silurian.
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Q 9. How Carbon dating helps in age determination?
Carbon (C) has three naturally occurring isotopes.
Both C-12 and C-13 are stable, but C-14 decays by
very weak beta decay to nitrogen-14 with a half-life
of approximately 5,730 years.
After the organism dies, The amount of C-14 is compared
to the amount of C-12, the stable form of carbon, to
determine how much radiocarbon has decayed, thereby
dating the artifact.
Q 10. Differentiate between Eon and Epoch.
Ans. Eon and Epoch are divisions of geological time scale
Eon: Two or more geological Eras form an Eon, which is the
largest division of geologic time, lasting many hundreds of
millions of years.
Epoch: An epoch is a division of a geologic period; it is the
smallest division of geologic time, lasting several million
years. Subdivision of periods into epochs can be done only
for the most recent portion of the geologic time scale. This
is because older rocks have been buried deeply, intensely
deformed and severely modified by long-term earth
processes. As a result, the history contained within these
rocks can not be as clearly interpreted.
Q11
Write a note on the Eocene life.
Ans. The first grasses appeared in the Eocene epoch .The grazing
mammals evolved the teeth enabling a diet of harsh grass. The
Eocene epoch was a period when flowering plants continued a
massive radiation that began in the Paleocene epoch. Many new
species of shrubs, trees and small plants appeared. A variety of
trees thrived in a warm Eocene climate, including beech, elm,
chestnut, magnolia, redwood, birch, and cedar, and more. The
evolution of plants was providing a powerful selective pressure
across the entire animal Kingdom, and many new symbiotic
systems appeared.
Q 12. Write an account on the Precambrian era
1)
Ans. The Precambrian time constitutes about 5/6
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of the total geological time and is characterised by the
appearence of life in simplest form. The total duration
of this eon ranges from 570 million years to 450 million
years. The first report of life in Precambrian belong to
algae like organisms, which was discovered by Tayler
et.al (1954) from Gunflint formation in western
Ontario. From the Samearea were discovered fossil
coccoid and bacilus type bacteria. Another microfossil
flora has been described from upper Pre cambrian
rocks at bitter springs, Central Australa. This chert
shows 50 species belonging to blue green algae,
bacteria, green algae and some fungi. Thus it has also
been called age of blue green algae.
Q13. Grand Canyon is a perfect time capsule, explain.
Ans. The Grand Canyon spectacularly exposes rocks spanning
hundreds of millions of years of Earth’s history. The oldest rocks
in the Grand Canyon are exposed at the base of the gorge and are
late Proterozoic. These rocks are overlain by younger Paleozoicage rocks. This is an example of superposition. Each major layer
of sedimentary rock in the Grand Canyon contains different types
of fossils.
Q14. What is absolute and relative dating?
Ans. Absolute dating is the process of determining an approximate
computed age in archaeology and geology. Absolute dating
provides a computed numerical age in contrast with relative
dating, which provides only an order of events. It involves
radiometric methods like carbon dating, Uranium, Lead method.
Relative dating of rocks and fossils from an area is based on
the Principle of Superposition, which enables scientists to put
historical events in order. Relating the succession of events in
one region to those in another requires that the two areas be
stratigraphically correlated. Correlations can be made by tracing
rock strata from one area to another by using the Principle of
Lateral Continuity or by relating the fossils of the two areas using
the Principle of Faunal Succession.
Q15. What do you mean by the principle of faunal
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succession?
Ans. This principle is based on the variation of fossils, viz.
actual remains, petrifications, compressions, microfossils,
incrustations, moulds, casts and imprints of different
organisms. William Smith (1700s) stated that different rock
layers contain particular types of fossilized flora and fauna, and
that these fossil forms succeed each other in a specific and
predictable order that can be identified over wide distances. Thus a fossilized Neanderthal bone will never be found in the
same stratum as a fossilized Megalosaurus, because Neanderthals
and Megalosauruses lived during different geological periods,
separated by many millions of years. This allows for strata to be
identified and dated by the fossils found within.