What is absolute vs relative dating? - ppt video online download
SWBAT differentiate absolute dating and relative dating Essential Questions? Compare and contrast absolute and relative dating. How are they the same?. Radiometric Dating- determining the absolute age of a sample based on the ratio of they gather information about the sequence and compare it to the geologic column. ObjectiveObjective Contrast relative dating with absolute dating. OBJECTIVES. • Define, compare, and contrast relative and absolute age dating. • Describe the development of ideas that led to the modern view of geologic time.
It is critical to first verify that the artifacts and fossils are in direct relation to one another.
Mostly used as a relative dating method because it takes so much effort to calibrate the sample. Most useful in dating human and animal skeletal remains. This idea is based on the concept that certain chemicals will build up in an object over time; the more of the chemical found in the material the older the remains.
These techniques are known as FUN techniques fluorine, uranium, and nitrogen tests. These three elements affect either the organic or hydroxyapetite in varying ways allowing us to measure and gain a relative date.
Three things can be determined: This technique was introduced in by a University of Chicago scientist Willard Libby. Living creatures regularly absorb c14 as well as c12 throughout that life at a constant rate. The half life for c14 is 5, years. Which means that it takes years for half of the amount of c14 in an organism to decay. It takes for another half of the remaining c14 to decay, etc.
So the age can be determined by comparing the proportion of c14 to stable c Radiocarbon dating has revolutionized archaeological dating. It provided the first means of relating dates and sequences on a worldwide basis. Yet, we now know that radiocarbon does have deficiencies.
We know that this method is only accurate in dating artifacts up to about 50, years ago. This is achieved when we uncover a tree or a portion of a tree in association with a site or from boards on structures found at archaeological sites, or artifacts manufactured from wooden items.
Douglas it is based on the idea that each year a new ring or row of wood cells grows. Often used as a check to radiocarbon dating.
C HAPTER 6 LESSON By: Kaylynn Priday Sam Davis. - ppt download
Scientists use different methods to determine the age of objects in sedimentary rocks. The bottom layers of rock are usually the oldest, and the top layers are usually the youngest. Scientists can use the order of rock layers to determine the relative age of objects within the layers. For example, fossils in the bottom layers are usually older than fossils in the top layers. To make relative dating easier, geologists combine data from all of the known rock sequences around the world.
From this information, geologists created the geologic column — an ideal sequence of rock layers that contains all of the known fossils and rock formations on Earth, arranging layers from oldest to youngest. Scientists who study past life are called paleontologists. Of course the real world is never quite so simple.
There are several different ways to destroy smaller craters while preserving larger craters, for example. Despite problems, the method works really, really well. Most often, the events that we are age-dating on planets are related to impacts or volcanism. Volcanoes can spew out large lava deposits that cover up old cratered surfaces, obliterating the cratering record and resetting the crater-age clock. When lava flows overlap, it's not too hard to use the law of superposition to tell which one is older and which one is younger.
If they don't overlap, we can use crater counting to figure out which one is older and which one is younger. In this way we can determine relative ages for things that are far away from each other on a planet. Interleaved impact cratering and volcanic eruption events have been used to establish a relative time scale for the Moon, with names for periods and epochs, just as fossils have been used to establish a relative time scale for Earth.
Absolute Dating Tuesday, December 2nd, 2014.
The chapter draws on five decades of work going right back to the origins of planetary geology. The Moon's history is divided into pre-Nectarian, Nectarian, Imbrian, Eratosthenian, and Copernican periods from oldest to youngest. The oldest couple of chronostratigraphic boundaries are defined according to when two of the Moon's larger impact basins formed: There were many impacts before Nectaris, in the pre-Nectarian period including 30 major impact basinsand there were many more that formed in the Nectarian period, the time between Nectaris and Imbrium.
The Orientale impact happened shortly after the Imbrium impact, and that was pretty much it for major basin-forming impacts on the Moon.
C HAPTER 6 LESSON 1-4 By: Kaylynn Priday Sam Davis.
I talked about all of these basins in my previous blog post. Courtesy Paul Spudis The Moon's major impact basins A map of the major lunar impact basins on the nearside left and farside right. There was some volcanism happening during the Nectarian and early Imbrian period, but it really got going after Orientale. Vast quantities of lava erupted onto the Moon's nearside, filling many of the older basins with dark flows. So the Imbrian period is divided into the Early Imbrian epoch -- when Imbrium and Orientale formed -- and the Late Imbrian epoch -- when most mare volcanism happened.
People have done a lot of work on crater counts of mare basalts, establishing a very good relative time sequence for when each eruption happened. The basalt has fewer, smaller craters than the adjacent highlands. Even though it is far away from the nearside basalts, geologists can use crater statistics to determine whether it erupted before, concurrently with, or after nearside maria did.
Over time, mare volcanism waned, and the Moon entered a period called the Eratosthenian -- but where exactly this happened in the record is a little fuzzy. Tanaka and Hartmann lament that Eratosthenes impact did not have widespread-enough effects to allow global relative age dating -- but neither did any other crater; there are no big impacts to use to date this time period.Dating Rocks with Fossils
Tanaka and Hartmann suggest that the decline in mare volcanism -- and whatever impact crater density is associated with the last gasps of mare volcanism -- would be a better marker than any one impact crater.
Most recently, a few late impact craters, including Copernicus, spread bright rays across the lunar nearside. Presumably older impact craters made pretty rays too, but those rays have faded with time. Rayed craters provide another convenient chronostratigraphic marker and therefore the boundary between the Eratosthenian and Copernican eras. The Copernican period is the most recent one; Copernican-age craters have visible rays.
The Eratosthenian period is older than the Copernican; its craters do not have visible rays.
Here is a graphic showing the chronostratigraphy for the Moon -- our story for how the Moon changed over geologic time, put in graphic form. Basins and craters dominate the early history of the Moon, followed by mare volcanism and fewer craters. Red marks individual impact basins. The brown splotch denotes ebbing and flowing of mare volcanism. Can we put absolute ages on this time scale? Well, we can certainly try. The Moon is the one planet other than Earth for which we have rocks that were picked up in known locations.
We also have several lunar meteorites to play with. Most moon rocks are very old. All the Apollo missions brought back samples of rocks that were produced or affected by the Imbrium impact, so we can confidently date the Imbrium impact to about 3.
And we can pretty confidently date mare volcanism for each of the Apollo and Luna landing sites -- that was happening around 3. Not quite as old, but still pretty old. Alan Shepard checks out a boulder Astronaut Alan B.
- Relative and Absolute dating Venn Diagram ( Block Diagram)
- What is absolute vs relative dating?
- Relative and absolute ages in the histories of Earth and the Moon: The Geologic Time Scale
Note the lunar dust clinging to Shepard's space suit. The Apollo 14 mission visited the Fra Mauro formation, thought to be ejecta from the Imbrium impact.
Beyond that, the work to pin numbers on specific events gets much harder.