Presentation on theme: "Chapter 21 Fossils & the Rock Records"— Presentation transcript:

NOTE - relative dating can only determine the sequential order in which a series of events occurred, not when they occur. State the Principle of superposition: The laws of nature operate today as they have in the past.


  • Presentation on theme: "Fossils and the Rock Record"— Presentation transcript:.
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The oldest rocks in an undisturbed sequence of rock layers will be at the bottom of the sequence. Reveals a million year old section of rock which was folded by a massive compression of the earth's crust some million years ago during formation of Pangaea , leading to the cut's distinctive "U" shaped fold which is called a syncline.

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Some type of disturbance. Any rock formation or fault is younger than the rock or feature that it cuts through.


  • 21.2: Relative Dating of Rocks;
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  • Fossils and the Rock Record.

You can't cut across something that isn't already there! Gaps in the rock record during which erosion occurred or deposition was absent.

What makes correlation useful? The remains or traces of organisms found in the geologic rock record The process of matching distinctive rock units from different regions is called correlation. Scientists can use fossils to match the ages of rock units around the world.

What is an index fossil? Fossils that lived for only a short time period but were widely spread throughout the world. Ammonites lived about million years ago.

Chapter 21 Fossils and the Rock Record

At these boundaries, fossils of certain life forms are no longer present and new life forms begin to appear. Each radioactive isotope, or radioisotope, has its own rate, expressed in terms of its half-life.

Half-life is the time taken for a substance or collection of particles to decay by half of its original amount. Geologic cross-sections represent a vertical slice taken through Earth.

Earth Science: Geology, the Environment, and the Universe

What does a geologic map show? Geologic maps show the horizontal surface distribution of various rock formations. First - The principle of original horizontality states that sediments are laid down in horizontal layers. Surface Water Section 9.

burrowmax.dev3.develag.com/portable-video-news-and-field-production.php The Nature of Storms Section Physical Oceanography Section The Marine Environment Section Plate Tectonics Section Volcanic Activity Section Mountain Building Section Fossils and the Rock Record Section The Precambrian Earth Section The Paleozoic Era Section The Mesozoic and Cenozoic Eras Section Earth Resources Section Energy Resources Section Human Impact on Earth Resources Section Our Solar System Section The Galaxies and the Universe Section To report a technical problem with this Web site, please contact the Web Producer.