Relative Dating

Starter 03/13/13Why do sedimentary rocks form layers?Directions1. Take a glass and fill it 1/2 full of water. This is the lake. Add a layer of one of the colors of sand or gravel. To model a dead organism, drop one of the sea shells in it next to the side of the glass so you can see it. It is now a fossil. 2. A flood fills the lake with new sediments. Add another color of sand or gravel to the lake. Add another sea shell for the new fossil.3. A wind storm carries a large amount of dust into the lake. Add another layer of sediment and a fossil.4. Draw and color a picture of your glass and label the fossils (give them a name of your choice) Then answer the questions.

Relative DatingRelative DatingRelative dating is a way to determine the order in which something happenedIt is based on two assumptions:That events in the past occurred in the same way that they do todaySedimentary rocks are stacked on Earths surface with the oldest layers on the bottom

Which layer is oldest?Relative DatingFlat layers of sedimentary rock do not stay flat for very long.These are some of the changes that can be made to flat layers of sedimentary rock1. Layers of Rock can be FOLDED!Pressure from inside Earth pushes outward, toward the surface.

2. Layers of Rock can be moved by FAULTS

3. Layers of Rock can be eroded by wind or water.

See how the upper layers have eroded so that this older white band is at the surface?4. Layers of Rock can be added to by sedimentation or deposition.

FoldingNew Layers5. Layers of rock can have magma seep into them. These are igneous intrusions.

Where is the igneous intrusion?

Can you see where the magma spread out from the vein?

Where is the intrusive igneous rock?It has GLUED the other rock together!Put the layers in order from OLDEST to YOUNGESTGHCEDFBADEFGHCIBAPut the layers in order from OLDEST to YOUNGEST

GBKDXR1. 2.3.4.5.6.7.8.Starter 03/15/13How are fossils formed?

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Meet the

Horses evolved about 55 million years ago.Meet these

Dinosaurs lived from about 230 million years ago, to 65 million years agothats nearly 160 MILLION YEARS!!!Meet the

Phoberomys pattersoni, or Ratzilla, lived in Venuzula about 8 million years agoMeet the

Trilobites appeared very early in Earths history but disappeared around 250 million years ago, when dinosaurs appeared on Earth

In which layer would we find each of these animals?8 mya0 mya250 mya160 mya

Fossil formationFossil formation involves deposition AND erosion!Step 1:Animal or Plant dies and sinks to the bottom of a body of water.

Fossil formationStep 2:The animal gets covered in sediment (the process of deposition!)

Fossil Formation

Step 2:The animal gets covered in sediment layers(the process of deposition!)Fossil FormationStep 3:The water evaporates and the animals body decays, leaving the skeleton. (The minerals in the rock around and above the animal make the skeleton harder)

Fossil FormationHow bones are made stronger by rock minerals

Fossil FormationStep 4:The pressure from the rock layers SQUISHES the skeleton and makes an indentation in the rock.

Fossil FormationStep 5:Erosion brings the skeleton closer to the surface so that we can find the fossil.

Fossil formationAnd what we see is this

MOLDCASTFossil Formation

MOLD

CASTFossil Formation

MOLDCAST

Fossil Formation

MOLDCAST

Fossil Formation

Some fossils are found as casts. Others are found as molds.

Which is which in this picture?MoldCastFossil Formation

CASTMOLDWhat is this?

Fossils show Changes over Time

Smaller eyebrow bonesThinner upper jawFossils show Changes over Time

Upper skull slopes backwardUpper jaw gets smaller

Fossils show Changes over Time

Skull is round instead of oval shapedCheek bones point up instead of outFossils show Changes over Time

Eyebrow bone nearly disappearsUpper jaw is almost flat, instead of sticking out

Fossils show Changes over Time

Eyebrow bone blends into skullSkull is round on top instead of flatLower jaw is less thick

Fossils show Changes over TimeHow might humans change in the future?What will our fossils look like in 100,000,000 years?