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The Thin Clay Line in the Ranch Creek

Grade 8 fossil record practice: read leaf, fern spore, dinosaur and mammal data from a ranch creek bank to find a mass extinction and the recovery after it.

Grade 8ScienceInteractive · Printable

Aligned toMS-LS4-1

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What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
9 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Matching, Short answer

About this worksheet

What students practice

Students read fossil data from dated rock layers to find patterns of extinction and recovery.
Students use fossil evidence to argue how life changed after a mass extinction.

How to use

Sketch the creek bank as a column of layers on the board, oldest at the bottom, and label the clay line before students read the graph and table.

Curriculum

NGSS standard covered

MS-LS4-1

Read the fossil record for patterns in the existence, diversity, extinction and change of life over Earth's history.

Preview

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Name Date

The Thin Clay Line in the Ranch Creek

Read a creek bank's fossils for extinction and recovery.

Part 1: Plants in the creek bank

Read the passage and the leaf graph, then answer the questions.

What the Flood Uncovered

1Solveig Haugen's family raises cattle and grows wheat on a ranch in western North Dakota. Two springs ago, a flood cut a steep new bank along the creek that runs through their pasture. The fresh bank showed stripes of gray, brown and tan rock, and Solveig found a fossil leaf pressed into one of them. Her parents called the state university, and a team led by paleontologist Dr. Imani Castellano got permission to study the bank. The bank is about 6 m tall, and its layers lie flat, one on top of another, with no folds or breaks.

2The team found a clay layer only about 1 cm thick running across the whole bank. Volcanic ash beds above and below it let the team date the layers, and the clay itself formed about 66 million years ago. A clay layer of the same age, with the same unusual chemistry, has been found at many sites around the world, and many scientists link it to a huge asteroid impact. The team named the layers below the clay L1 to L3, from the bottom up, and the layers above it L4 to L6.

3In each layer, the team counted how many different kinds of flowering-plant leaves they found. They also dissolved small rock samples in the lab to free tiny pollen grains and fern spores, and counted what percent of all the grains were fern spores. Fern spores are easy to tell apart from pollen under a microscope. Today, ferns are often among the first plants to grow back on bare ground after a volcano erupts or a forest burns.

4The team also searched each layer for bones and teeth. Below the clay they dug up bones of large dinosaurs, including horned and duck-billed kinds. Because birds are a living group of dinosaurs, the team listed these bones as non-bird dinosaurs. They also screened the rock for the tiny teeth of mammals, most of which were no bigger than mice or rats, and counted how many different kinds of mammals the teeth came from. To keep the counts fair, the team searched each layer for the same number of days and sieved the same amount of rock from each one.