Types of relative dating

Locally, physical characteristics of rocks can be compared and correlated.On a larger scale, even between continents, fossil evidence can help in correlating rock layers.By matching partial sequences, the truly oldest layers with fossils can be worked out.By correlating fossils from various parts of the world, scientists are able to give relative ages to particular strata. Relative dating tells scientists if a rock layer is "older" or "younger" than another.For example, most limestones represent marine environments, whereas, sandstones with ripple marks might indicate a shoreline habitat or a riverbed.Return to top The study and comparison of exposed rock layers or strata in various parts of the earth led scientists in the early 19th century to propose that the rock layers could be correlated from place to place.

The first card in the sequence has "Card 1, Set A" in the lower left-hand corner and represents the bottom of the sequence.INTRODUCTION Scientists have good evidence that the earth is very old, approximately four and one-half billion years old.Scientific measurements such as radiometric dating use the natural radioactivity of certain elements found in rocks to help determine their age.The fossils represented by the letters on this card are "younger" than the "T" or "C" fossils on the "TC" card which represents fossils in the oldest rock layer.Sequence the remaining cards by using the same process.PALEONTOLOGY, AND in particular the study of dinosaurs, is an exciting topic to people of all ages.Although most attention in today's world focuses on dinosaurs and why they became extinct, the world of paleontology includes many other interesting organisms which tell us about Earth's past history.If the letters "T" and "C" represent fossils in the oldest rock layer, they are the oldest fossils, or the first fossils formed in the past for this sequence of rock layers. Now, look for a card that has either a "T" or "C" written on it.Since this card has a common letter with the first card, it must go on top of the "TC" card.These major concepts are part of the Denver Earth Science Project's "Paleontology and Dinosaurs" module written for students in grades 7-10.The module is an integrated unit which addresses the following National Science Education Standards: *Science as Inquiry: Students develop the abilities necessary to do scientific inquiry — identify questions, design and conduct scientific investigations, use appropriate tools and technologies to gather, analyze and interpret data, think critically and logically to make the relationships between evidence and explanations, communicate results, and use mathematics in all aspects of scientific inquiry.

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