ACTIVITY: download as pdf file

Choose the method of data collecction that you will use with your students.  (calcualtor or computor)  Print out a copy of the appropriate lab for each student.

Prelab

Discuss what factors affect collecting sonar data? - Does the motion of the ship have any affect on the data? - How far can sonar pulses travel? A crewmember received an interesting email message while we were in the Bransfield Straight. A friend aboard a Navy submarine in transit sent a message that stated that our active sonar was so loud it was driving them crazy. They were many miles away from the ship. They never gave a precise position - Why it is important to know what's below the ice or the sea?

Do some hands-on modeling of the reflection of waves (Slinkies, etc.) A quick introduction to the fundamentals of sonar is a classic activity/demonstration where students measure the time for an echo. Have students measure a distance of about 50 meters away from a large solid two story or higher wall. Use a couple of boards slapped together to produce a loud sound wave. Have students record the length of time it takes from the moment the sound is made to the time that they hear the returned echo. Sonar works by measuring the echo time. This gives you an opportunity to discuss the importance of knowing temperature and density medium, because these affect the speed at which sound travels. (Distance = speed of sound x echo time/2)

When doing Antarctic research, the temperature and salt concentration are constantly measured. The water actually increases in temperature with depth. To measure distances under these conditions you have to use an average of temperature to make your measurements. Another problem about working in Antarctica is that the sound waves travel in all directions. Sound reflected from sea ice and icebergs creates noise that must be removed either manually or electronically to an accurate view of the seafloor can be made.

It is important that when you set up the hidden surface, have a parcticular feature those students need to find. This gives you an opportunity to assess their data interpretation skills and is a good practical evaluation tool.

Elaboration

Present to your students the following ideas for discussion.

Ask students how they think researchers know what type of topography is hidden by ice or water. Students might suggest the following:

·  They drill holes in the ice.

·  They send divers down to make maps.

·  They use submarines.

·  Etc…

Explain that researchers can use sound waves to explore hidden surfaces. Ask students how they think this is possible. Students may know that bats and dolphins use echolocation to figure out where they are. If they mention this, ask them to explain how echolocation works. Students should be able to say that these animals send out sound waves and these waves bounce off of objects and travel back to the animals.

Evaluation:

Skill

Level 1

Level 2

Level 3

Setup and Report Design

Teacher assisted. Group needs step by step help to complete.

Report and activity setup with minor support and encouragement from teacher.

Setup and report is done within group. Teacher interaction is for confirmation and clarification.

Graphing and Analysis

Graphs have been made. Analysis is incomplete or incorrect.

Graphs are complete and properly labeled. Analysis is mostly correct with minor errors.

Graphs and analysis are thorough, complete and correct.

Activity Report

Parts of the report are missing, poorly labeled, lack organization.

All components present, organization needs improvement.

All components present, well organized, neat, spelling and grammar also correct.

Unknown Seafloor

Student has collected data, but has not completed graphs or interpreted data.

Data has been collected and preliminary graphs are prepared without interpretation.

Data and graphs are complete and well organized. Students are able to identify unknown objects from their data and graphs.