Materials: two sets of sequence cards in random order (set A: nonsense syllables; set B: sketches of fossils), pencil, paper Procedure Set A: 1) Spread the cards with the nonsense syllables on the table and determine the correct sequence of the eight cards by comparing letters that are common to individual cards and, therefore, overlap.The first card in the sequence has "Card 1, Set A" in the lower left-hand corner and represents the bottom of the sequence.
Time factors of millions and billions of years is difficult even for adults to comprehend.However, "relative" dating or time can be an easy concept for students to learn.Scientists also use direct evidence from observations of the rock layers themselves to help determine the relative age of rock layers.Specific rock formations are indicative of a particular type of environment existing when the rock was being formed.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.
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.
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.
INTRODUCTION Scientists have good evidence that the earth is very old, approximately four and one-half billion years old.