Only have 22.00 dollars1.) For our Week 7 Written Assignment, we will be using the made-up scenario provided above for working with the “best applications of numerical dating techniques for a log buried in a Holocene flood and a Permian felsic volcanic unit.” These examples will allow us to practice using the geologic time scale from our textbook on page 293 (Figure 9.24) and work with the dating techniques. Make sure to notice that the time scale on the right of the figure is a section being blown up of the time scale on the left side of the figure. Also be sure to look at the title of each column – Eon, Epoch, Period, etc. – this will be relevant when answering the questions. All the information you will need for this assignment is in our textbook and lecture material, therefore there is no need for any additional sources.The attachment have the page 293 (Figure 9.24)
2.) ***Remember to always label the time scale that you are using when answering these questions below. A time scale label example is thousands of years ago, days old, minutes old, billions of years ago, etc.***
3.) Geologic Time Scale Practice: a.What is the age label for the geologic time scale we are using (refer to the far right column)? This is what MYA stands for.b. The numerical age range of the Mesozoic Era is 251 million years ago to 65.5 million years ago per the geological time scale on page 293 of our textbook. What is the numerical age range of the Cambrian Period? c.What is the name of the Eon with the numerical age range of 2,500 – 542 million years ago? REMEMBER: the answer is in the EON column – each column is a different type of age category.
d. What is the name of the Era that covers the time age range from 65.5 million years ago to the present? e. What is the oldest numerical age listed on this time scale? Give the number.
4.) Our made-up example states that there is “a log buried in a Holocene flood,” which came first – the log or the flood? Essentailly, think of which item had to be present first in order for the other item to ‘bury’ the first item.
5.) What is the numerical age range of the Holocene Epoch?
6.) What is the main element that the tree is made of? This is one element from the Chemical Periodic Table, An example of an element is H (for hydrogen) or Sn (for tin) – now which element is the main one in trees? Check out the periodic table here http://periodic.lanl.gov/index.shtml
7.) Now that you know what numerical age range the log is from, and what material the log is made of – take these two pieces of information to decide on one type of numerical dating technique that would work to date the log. REMEMBER: Be specific – don’t just say radiometric dating – because there are many types of radiometric dating methods – pick one covered in the book.
8.) Give two reasons why you chose the numerical dating technique that you did in question 7 for the log.
9.) What is the numerical age range of the Permian Period?
10.) What type of rock is a Felsic Volcanic Unit – it is one of the three rock types from the rock cycle we reviewed in week 3? We know that a felsic volcanic rock is more than 65% Silica and includes large amounts of Aluminum, Potassium and Sodium, thus meaning it is highly viscous. REMINDER: the answer is one of the three rock types in the rock cycle
11.) Now that you know what numerical age range of the Permian Period and what type of rock the Felsic Volcanic Unit is,– take these two pieces of information to decide on one type of numerical dating technique that would work for this rock in this scenario. NOTE: Be specific – just don’t day radiometric dating – it is all radiometric dating – the book covers specific methods – pick one of those.
12.) Give two reasons why you chose the numerical dating technique that you did in question 11 for the rock.
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The geologic time scale subdivides the 4.6-billion-year history of Earth into many different units
and provides a meaningful time frame within which the events of the geologic past are arranged.
As shown in Figure 9.24, eons represent the greatest expanses of time. The eon that began about
542 million years ago is the Phanerozoic, a term derived from Greek words meaning “visible
life.” It is an appropriate description because the rocks and deposits of the Phanerozoic eon
contain abundant fossils that document major evolutionary trends.
Another glance at the time scale reveals that eons are divided into eras. The Phanerozoic eon
consists of the Paleozoic era (paleo= ancient, zoe = life), the Mesozoic era (meso =
middle, zoe = life), and the Cenozoic era (ceno = recent, zoe = life). As the names imply, these
eras are bounded by profound worldwide changes in life-forms.*
Major changes in life-forms are discussed in Chapter 22.
Figure 9.24 Geologic time scale
Numbers on the time scale represent time in millions of years before present. Numerical dates
were added long after the time scale was established using relative dating techniques. The dates
on this time scale are those currently accepted by the International Commission on Stratigraphy
(ICS) in 2014. The color scheme used on this chart was selected because it is similar to that used
by the ICS.
Each era of the Phanerozoic eon is further divided into time units known as periods. The
Paleozoic has seven, and the Mesozoic and Cenozoic each have three. Each of these periods is
characterized by a somewhat less profound change in life-forms as compared with the eras.
Each of the periods is divided into still smaller units called epochs. As you can see
in Figure 9.24, seven epochs have been named for the periods of the Cenozoic. The epochs of
other periods usually are simply termed early, middle, and late.
Notice that the detailed portion of the geologic time scale does not begin until about 542 million
years ago, the date for the beginning of the Cambrian period. The nearly 4 billion years prior to
the Cambrian are divided into two eons, the Archean (archaios = ancient) and
the Proterozoic (proteros = before, zoe = life). It is also common for this vast expanse of time to
simply be referred to as the Precambrian. Although it represents about 88 percent of Earth
history, the Precambrian is not divided into nearly as many smaller time units as the Phanerozoic
Why is the huge expanse of Precambrian time not divided into numerous eras, periods, and
epochs? The reason is that Precambrian history is not known in great enough detail. The quantity
of information that geologists have deciphered about Earth’s past is somewhat analogous to the
detail of human history. The further back we go, the less that is known. Certainly more data and
information exist about the past 10 years than for the first decade of the twentieth century; the
events of the nineteenth century have been documented much better than the events of the first
century C.E.; and so on. So it is with Earth history. The more recent past has the freshest, least
disturbed, and most observable record. The further back in time a geologist goes, the more
fragmented the record and clues become. Other reasons to explain our lack of a detailed time
scale for this vast segment of Earth history include:
The first abundant fossil evidence does not appear in the geologic record until the beginning
of the Cambrian period. Prior to the Cambrian, simple life-forms such as algae, bacteria,
fungi, and worms predominated. All of these organisms lack hard parts, an important
condition favoring preservation. For this reason, there is only a meager Precambrian fossil
record. Many exposures of Precambrian rocks have been studied in some detail, but
correlation can be difficult when fossils are lacking.
Because Precambrian rocks are very old, most have been subjected to a great many changes.
Much of the Precambrian rock record is composed of highly distorted metamorphic rocks.
This makes it difficult to interpret past environments because many of the clues present in the
original sedimentary rocks have been destroyed.
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