Dating Differences Defined Absolute vs. Relative Dating

Relative Dating A method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock

Absolute Dating Any method of measuring the age of an event or object in years

Activity – Model List 5 important events in your life (the one at the bottom should be the oldest!! Started working at Wendell Middle Started working at Southwest Middle Graduated from Southeastern University Started work at Lakeland High School Graduated from high school Got Braces Born December 2014 August 2013 May 2013 January 2013 June 2008 September 2004 November 1990

Radioactive dating Measurement of the amount of radioactive material (usually carbon 14) that an object contains; a form of absolute dating

Uranium A white, radioactive metallic chemical element that weighs more than any other element in nature; used in radioactive dating

BrainPop See how radioactive dating works by watching this brainpop: Carbon Dating

8th Grade Science Spring 2015 Rock Layers 8th Grade Science Spring 2015

Rock Layer The four rock columns were found at the places indicated by letters A, B, C, D. Different rock layers are found on the surface at these places.  The problem is to find which layers match. Color the matching sections from A, B, C, and D the same color. Cut out the columns of rock layers. Arrange the columns of rock layers side by side by matching layers.

Do not write what is in purple or teal Write the following notes on the BACK of your Rock Layers Activity Title: The Law of Superposition

The Law of Superposition 8th grade science Spring 2015

Law of Superposition States that the oldest rocks lie on the bottom and the youngest rocks are on top of any undisturbed sequence of sedimentary rocks.

Correlation Matching rock layers in different locations to see if they formed at the same time and under the same conditions

Unconformity A gap in the rock record What could cause an unconformity? Erosion could cause rock to be worn away and “disappear” When plates move together (convergent boundary) one plate “disappears”

Rock Layers Analysis Questions Flip back over to the Rock Layers side and answer the following questions on that side. 1. Which rock layer is the oldest? The youngest? 2. Which fossil is the oldest? The youngest? 3. What happened to the layer in rock strip C? (Where did it go?) Use your vocabulary words to describe what happened to layer in rock strip C.

Sedimentary Rock Most fossils are found in Sedimentary Rock Rock that forms when sediments are compacted and cemented together

Index Fossil A fossil of an organism that is known to have lived in a particular geologic age that can be used to date the rock layer in which it is found A key example of an organism used as an index fossil are TRILOBITES, a group of hard-shelled animals whose body had three sections, lived in shallow seas, and became extinct about 245 million years ago

Other Clues to Relative Age Clues From Igneous Rock Lava that cools at the surface is called an extrusion Rock below an extrusion is always older.

Magma that cools beneath the surface is called an intrusion An intrusion is always younger than the rock layers around and beneath it Extrusion Intrusion

The Cross-Cutting Law Faults (a break in the rock) are always younger than the rock it cuts through! Fractures (a crack in the rock) are always younger than the rock it cuts through The arrow points to a fault – notice the layer of white rocks do not line up with each other

To Summarize Generally, the top layer is the youngest – bottom layer is the oldest The rocks below an extrusion (lava at the top) are always older than the extrusion The intrusion (lava within the rocks) is always younger than the rocks around it A fault is younger than the rocks around it

Using your knowledge of the Law of Superposition, put the following layers in order from the youngest to the oldest. E YOUNGEST _______ _______ OLDEST _______ D A B C

Practice You have two other examples on your worksheet – try to put the rock layers in order from youngest to oldest

Items to STUDY for Tomorrow’s Quiz Examples of Mechanical and Chemical Weathering Vocabulary Definitions: Relative Dating, Absolute Dating, Radioactive Dating, Uranium, Correlation, Unconformity, Sedimentary Rock, Index Fossil Law of Superposition Where are the oldest/youngest rock layers? What are intrusions, extrusions, faults and fractures?