The Launch PadThursday, 12/2/10
List four examples of indirect fossil evidence.
Tracks
Burrows
CoprolitesGastroliths
The Launch PadThursday, 12/2/10
The Principle of Fossil Succession states that:
fossils succeed one another in a
definite and determinable
order.
The Launch PadThursday, 12/2/10
Index fossils work on the premise that:
although different sediments may look different depending on the conditions under
which they were laid down, they may include the remains of the same species of
fossil.
Assignment Currently Open Pages Date of Notes
on Website Date Issued Date Due
Five Multiple Choice
Questions on Plate Tectonics
11/11 11/12
Project – Decade
Volcanoes11/15 11/19
Project – Killer Earthquakes
11/17 12/1
Project – Greatest
Mountains11/19 12/3
Radioactivity and Radiometric Dating A Quick Review of Atomic
Structure There are two main regions of an atom:
the nucleus, containing positively-charged protons
and neutral neutrons. the electron cloud,
containing negatively-charged electrons orbiting
the nucleus.
A Quick Review of Atomic Structure
An element’s identifying number is its atomic number, the number of protons in the atom’s nucleus
An element's mass numberis the number of protons plus
(added to) the number of neutrons in the atom’s nucleus.Isotopes are atoms of the same
element that have different numbers of neutrons and therefore different mass
numbers.
Radioactivity and Radiometric Dating
Radioactivity Radioactivity refers to the particles and energy which
are emitted from nuclei as a result of nuclear instability.
Radioactivity and Radiometric Dating
Because the nucleus experiences the intense conflict between the two strongest forces in nature
(electromagnetism and the strong nuclear force), it should not be surprising that there are many nuclear
isotopes which are unstable and emit some kind of radiation.
Radioactive Decay Radioactive decay is the spontaneous
disintegration of a nucleus into a slightly lighter nucleus, accompanied by emission of particles,
electromagnetic radiation, or both.
The most common types of radioactive decay are alpha, beta, and gamma radiation.
Radioactivity and Radiometric Dating
Types of Radioactive Decay Alpha emission results in the release of an alpha particle, which consists of two protons and two neutrons bound
together.Alpha particles are helium nuclei and have a charge of 2+.
Radioactivity and Radiometric Dating
Types of Radioactive Decay Beta emission occurs when an elements
are unstable because they have too many neutrons.
To decrease the number of neutrons, a neutron can be converted into a proton
and an electron.The electron is emitted from the nucleus
as a beta particle.A beta particle is an electron emitted
from the nucleus during some kinds of radioactive decay.
Radioactivity and Radiometric Dating
Types of Radioactive Decay Gamma emission occurs when gamma rays, (highest-energy
electromagnetic waves) are emitted from a nucleus as it changes from an excited state to a ground energy state.
Radioactivity and Radiometric Dating
Parent and Daughter IsotopesAn unstable (radioactive) isotope of an
element is called the parent. The isotopes resulting from the decay of the parent are called the daughter isotopes
(or products.)
Radioactivity and Radiometric Dating
parent
daughter
Radiometric Dating
Half-life is the time required for half of
the atoms of a radioactive sample
to decay.This technique yields
numerical data for the age of rocks and
fossils.
Radioactivity and Radiometric Dating
Carbon-14 Dating Carbon-14 is the radioactive isotope of carbon. C-14 is constantly produced in Earth’s upper atmosphere as a
consequence of cosmic ray bombardment. Cosmic rays are high-energy particles that shatter the nuclei of gas atoms,
releasing neutrons. Some of the neutrons are absorbed by nitrogen atoms, causing their nuclei to emit a proton. As a result, the atomic number decreases by one (7 – 6), and a
different element, carbon-14, is created.This isotope of carbon quickly becomes incorporated into carbon dioxide, which circulates in the atmosphere and is absorbed by living matter. As a result, all living organisms
contain a small amount of C-14, including you!
Radioactivity and Radiometric Dating
Carbon-14 Dating While an organism is alive, the decaying C-14 is constantly
replaced, and the proportions of C-14 and C-12 remain constant. C-12 is the stable and most common isotope of carbon.
However, when any plant or animal dies, the amount of C-14 gradually decreases as it decays to nitrogen-14 by beta emission.
By comparing the proportions of C-14 to C-12 in a sample, the age of the sample can be determined.
Carbon -14 has a half-life of only 5,730 years, so it can only be used to date relatively recent events.
C-14 dating has become a useful tool for paleontologists, anthropologists, archaeologists, historians, and geologists who
study very recent Earth history.
Radioactivity and Radiometric Dating
Project - FossilsYour presentation on fossils should
include the following:
Definition of “fossil”, definition of “paleontology”, the eight general types of
fossils, the fours types of indirect fossil evidence, the conditions that favor fossil preservation, summary of the Principle of
Fossil Succession, and definition of the term “index fossil”, and how they’re used.
NOTE: All topics must be illustrated!
You can do this on a sheet of paper, or electronically using Open Office Impress (send this to my e-mail).