Author:
Kristin Robinson
Subject:
Reading Informational Text
Material Type:
Homework/Assignment
Level:
Middle School
Tags:
License:
Creative Commons Attribution
Language:
English
Media Formats:
eBook, Graphics/Photos, Text/HTML

Education Standards (7)

Underwater Clues to a Buried Village

Underwater Clues to a Buried Village

Overview

What secrets about the past could a small lake hold?

Underwater Clues to a Buried Village

Crawford Lake is a small, deep lake west of Toronto. Lakes of this kind, called “meromictic lakes,” are found all over the world. But they are rare and of special interest to many scientists. Why?

Photo of a lake surrounded by rocks and mountains.
Investigating below the surface can reveal clues to the past.

In most lakes, all the water mixes together and churns up the mud on the bottom. In meromictic lakes, the water is so deep that it doesn’t get disturbed. Things that fall into the lake sink to the bottom, pile up and stay there for thousands of years in layers that you can see. Because of this, palaeobotanists (scientists who study fossilized plants) can take samples of bottom mud and find out about the plants that lived on the shores of the lake long ago.

That’s just what was happening at Crawford Lake in 1971. A palaeobotanist decided to collect a sample of bottom mud in order to study the pollen grains it contained. By looking at the fossilized pollen in the lake mud, he hoped to learn what plants had grown near the lake for hundreds of years and how they had changed.

To collect bottom mud, the botanist filled a heavy hollow tube with dry ice to make it freezing cold. He lowered this “frigid finger” into the lake and into the mud. When he pulled it up ten minutes later, it was coated with a thin crust of frozen mud.

Back at the lab, the botanist and his assistant studied the frozen crust. They could see layers, two for each year. The top two layers were from 1971. The further down they went, the older the layers and the pollen were. 

Then they found something unusual. The mud layers that were about 530 years old were loaded with corn pollen. At first, the botanist didn’t believe it. Why would corn pollen suddenly show up in the middle of a forest? Had native people lived on the shores of the lake, cut down the trees and planted corn fields? The botanist went to an archaeologist for help. 

How do you find the remains of a settlement that disappeared long ago? If you’re an archaeologist, you look for signs that people have somehow changed the land—telltale ridges or bumps or hollows. You watch for artifacts dug up by groundhogs or by a farmer’s plow. And you go to people who know the land better than you do—like farmers.

It turned out that the farmer who had lived on the shores of Crawford Lake had collected a basketful of stone axes and arrowheads on his land. He’d found most of them in his barnyard. Sure enough, when archaeologists dug up the barnyard, they found pottery, food storage pits, stains from old firepits and marks in the earth from long house posts. And in the garbage pits, they found charred kernels of corn! The botanist’s guess was right. Native people had once lived on the shores of the lake and had grown corn.

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