Download Our experiment was making a mold and then it turning out to be a cast

Brianna Schneider
Period #1
1-22-06
Word count:458
Our experiment was to make a mold of a fossil and then use plaster to turn it into
a cast. We used a pastry dish and put sand in it. Then we took a fossil and made an
imprint in the sand. After that we poured plaster into the cast. We let it dry for a day and
then the next day we took the cast of the fossil out of the mold. Then we took a toothpick
and scraped some of the sand off so that we could see the details of the fossil better.
Absolute age of a rock is the number of years since the rock formed. Relative age
of a rock is its age compared to the ages of other rocks. The difference between them is
that one (absolute age) is the number of years since the rock formed and one (relative
age) is the age compared to the ages of other rocks.
Radioactive dating is when scientists first measure the amount of a radioactive
element (the “parent” isotope) in the minerals that are in a rock. Then they measure the
amount of the stable element into which the radioactive element decays (the “daughter”
isotope). Radioactive dating is used by geologists to determine the absolute age of a rock.
The geologic time scale is a record of the geologic events and the life forms in
Earth’s history. The units of the geologic scale are eras, periods, and epochs. Eras are the
three long units of time. They are the Paleozoic Era, the Mesozoic Era, and the Cenozoic
Era. Periods are eras subdivided into units of geologic time. The Mesozoic Era has three
periods the Cretaceous Period, Jurassic Period, and the Triassic Period. There is only one
period in the Cenozoic Era. It is the Tertiary Period. On the other hand there are six
periods in the Paleozoic Era. They are the Permian Period, Carboniferous Period,
Devonian Period, Silurian Period, Ordovician Period, and the Cambrian Period. Epochs
are further subdivided periods of the Cenozoic Era.
I leaned a lot more about fossils and about rocks. I learned about the different
eras, periods, and epochs. I learned that there are three eras and that there are 10 periods
in all. I learned that there was one period in the Cenozoic Era, three in the Mesozoic Era,
and six in the Paleozoic Era. I also learned how to make a cast using sand, a fossil, and
some plaster. I also learned how scientists determine the age of a rock. They determine its
age by using index fossils. Index fossils are a fossil that must be widely distributed and
represent a type of organism that existed only for a short time.