Dating fossils worksheet answers

dating fossils worksheet answers

Instead, other methods are used to work out a fossil’s age. These include radiometric dating of volcanic layers above or below the fossils or by comparisons to similar rocks and fossils of known ages.

Knowing when a dinosaur or other animal lived is important because it helps us place them on the evolutionary family tree. Accurate dates also allow us to create sequences of evolutionary change and work out when species appeared or became extinct.

Where possible, several different methods are used and each method is repeated to confirm the results obtained and improve accuracy. Different methods have their own limitations, especially with regard to the age range they can measure and the substances they can date. A common problem with any dating method is that a sample may be contaminated with older or younger material and give a false age. This problem is now reduced by the careful collection of samples, rigorous crosschecking and the use of newer techniques that can date minute samples.

Volcanic rocks – such as tuff and basalt  – can be used in dating because they are formed at a particular moment in time, during an eruption. Sedimentary rocks are rarely useful for dating because they are made up of bits of older rocks.

Uranium is present in many different rocks and minerals, usually in the form of uranium-238. This form of uranium usually decays into a stable lead isotope but the uranium atoms can also split – a process known as fission. During this process the pieces of the atom move apart at high speed, causing damage to the rock or mineral. This damage is in the form of tiny marks called fission tracks. When volcanic rocks and minerals are formed, they do not contain fission tracks. The number of tracks increases over time at a rate that depends on the uranium content. It is possible to calculate the age of a sample by measuring the uranium content and the density of the fission tracks.

The age of volcanic rocks and ash can be determined by measuring the proportions of argon (in the form of argon-40) and radioactive potassium within them. Each volcanic eruption produces a new deposit of ash and rock. Fossils and other objects that accumulate between these eruptions lie between two different layers of volcanic ash and rock. An object can be given an approximate date by dating the volcanic layers occurring above and below the object.

Argon is gas that gradually builds up within rocks from the decay of radioactive potassium. It is initially formed in the molten rock that lies beneath the Earth’s crust. The heat from a volcanic eruption releases all the argon from the molten rock and disperses it into the atmosphere. Argon then starts to re-accumulate at a constant rate in the newly formed rock that is created after the eruption.

Examine the stratigraphic column diagram. What relationship seems to exist between the approximate age of the fossils and rocks layers and their depth in the earth?

Tectonic activity left some areas of land uplifted , and erosional forces from the lake, nearby rivers, and other forms of weathering exposed rock, even older rock layers, as outcroppings in the landscape. This made the fossils easier for researchers to find. The volcanic material in tuff layers also makes it possible to get a more accurate date for the fossils.

Potassium-argon dating is a form of isotopic dating commonly used in archaeology. Scientists use the known natural decay rates for isotopes of potassium and argon to find the date of the rocks. The radioactive isotope converts to a more stable isotope over time, in this case decaying from potassium to argon. If scientists find the ratio of potassium to argon, it tells them how long the rocks have been around by how long the isotopes have been decaying. By understanding the dates of these rocks, scientists can deduce the age of the nearby fossils.

Because each name is a unique identification, this helps scientists keep track of where and in what order fossils are found. Doing this helps paleontologists maintain accurate records and piece together the story of human history. In this example, the prefix "KNM-ER" tells us the relative location of where this fossil was found; this stands for Kenya National Museum—East Rudolf, from the former name of Lake Turkana. The accompanying numbers are chronological , meaning that, in this example, our fossil is the 1,813th fossil found in the area.

tribe of the hominid family of primates, distinguished by erect posture, bipedal movement, large cranial capacity, and use of specialized tools. Human beings are the only living hominins.

method of dating material such as rocks that compares the amount of a naturally occuring isotope of an atom and its decay rates. Also called radioactive dating.

atom with an unbalanced number of neutrons in its nucleus (isotope) that is radioactive, or decays by emitting particles from its nucleus. Also called a radionuclide.



DATING FOSSILS - Fact Monster

Examine the stratigraphic column diagram. What relationship seems to exist between the approximate age of the fossils and rocks layers and their depth in the earth?

Tectonic activity left some areas of land uplifted , and erosional forces from the lake, nearby rivers, and other forms of weathering exposed rock, even older rock layers, as outcroppings in the landscape. This made the fossils easier for researchers to find. The volcanic material in tuff layers also makes it possible to get a more accurate date for the fossils.

Potassium-argon dating is a form of isotopic dating commonly used in archaeology. Scientists use the known natural decay rates for isotopes of potassium and argon to find the date of the rocks. The radioactive isotope converts to a more stable isotope over time, in this case decaying from potassium to argon. If scientists find the ratio of potassium to argon, it tells them how long the rocks have been around by how long the isotopes have been decaying. By understanding the dates of these rocks, scientists can deduce the age of the nearby fossils.

Because each name is a unique identification, this helps scientists keep track of where and in what order fossils are found. Doing this helps paleontologists maintain accurate records and piece together the story of human history. In this example, the prefix "KNM-ER" tells us the relative location of where this fossil was found; this stands for Kenya National Museum—East Rudolf, from the former name of Lake Turkana. The accompanying numbers are chronological , meaning that, in this example, our fossil is the 1,813th fossil found in the area.

tribe of the hominid family of primates, distinguished by erect posture, bipedal movement, large cranial capacity, and use of specialized tools. Human beings are the only living hominins.

method of dating material such as rocks that compares the amount of a naturally occuring isotope of an atom and its decay rates. Also called radioactive dating.

atom with an unbalanced number of neutrons in its nucleus (isotope) that is radioactive, or decays by emitting particles from its nucleus. Also called a radionuclide.