In this lab activity, students determine density differences of water samples with varying temperature and salinity levels. Students synthesize information to predict the effects of oil in given water samples.

This hands-on lab activity is designed to teach students about how density differences, due to salinity, drive the flow of currents in the ocean. It also helps develop skills in performing and designing simple laboratory measurements; data entry, calculations and graph plotting in a spreadsheet; and comparing experimental data with a theoretical equation.
Key words: ocean circulation; density driven flows; salinity; ocean density; thermohaline circulation.

Density, Isostasy, and Topography Anne Egger, Stanford University The original activity Density, Isostasy, and Topography already exists within the SERC website. This page describes how this activity can be used ...

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HideA critical component of this activity involves sharing team data with the entire class, done the old-fashioned way on the chalkboard. Details This activity begins with an exploration of a topographic map of the earth, ending with the question: Why is the distribution of topography on the earth bimodal? The students then collect two forms of data. They measure the density of the most common rocks that make up oceanic crust (basalt), continental crust (granite), and the mantle (peridotite). They also measure the density of several different kinds of wood, and how high each kind floats in a tub of water. In each case, they work in teams of two or three and then the entire class shares their data. Based on the data from the wood, they derive an equation that relates the density of the wood to the height at which the block floats in the water - the isostasy equation. They then substitute density values for real rocks into their equation to derive thicknesses for average continental and oceanic crust, and apply their knowledge in order to draw a cross-section of the crust across South America. This activity gives students a real, hands-on and mathematical understanding of the principle of isostasy.

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These two hands-on labs are about the role of temperature and salinity in governing the density of seawater, a major factor controlling the ocean's vertical movements and layered circulation. In the first activity students work in groups to determine the density of tap water and of tap water with salt, then compare the densities. The second activity investigates the role of temperature and salinity in determining seawater density. Students use a Temperature-Salinity (T-S) Diagram to examine the effect of mixing on density. A list of key concepts, essential questions, common preconceptions and more is included. These are part of the Aquarius Hands-on Laboratory Activities.

In episode seven of the Beyond Penguins and Polar Bears podcast series, learn how scientists can get a first-hand look at changing polar icebergs and glaciers and what these changes can teach us about density.

River and wind processes can be readily studied in the field, and we have devised a series of lab exercises in western Nevada that take advantage of our rivers and deserts. But for density-contrast flows, there was no easy way to get the students beyond pictures and formulae. With the assistance of Tripp Plastics, we designed acrylic tanks that fit on a lab bench. They have a ramp with screw-adjustable slope up to 20Â. Students mix a solution of Epsom salt (MgSO4) to several experimental densities. They add a dye to make the dense fluid visible. The dyed fluid is released at the top of the slope. The grid allows the flow to be accurately timed and described. The students determine how density changes and how slope affect the flow velocity and structure.

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This activity modifies a typical density laboratory exercise to fit within a lecture session. Students are asked to compare the densities of six different rocks/minerals collected from six different environments. Based on the brief description of each rock the students are asked to first predict which rock has the highest density and which rock has the lowest density. The students are then asked to construct a hypothesis and test their hypothesis by calculating the density of the rocks. Students are then asked to apply information from lecture to place each rock in the appropriate layer of the Earth.

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This module addresses the problem of how to determine the density of the earth and has students do some field experiments to get the data they need to answer the problem.

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In this activity, students measure the densities of samples of granite, basalt, peridotite/dunite, and an iron meteorite, which are used as representatives of the various layers of the Earth (crust, mantle, core). The samples are weighed to determine their mass, and the Archimedes Principle is used to determine volume. From these two properties, they calculate density, compare it to accepted values presented in the discussion, and answer questions about their observations.

This module addresses the problem of how to determine the size of a ton of rocks of a given composition and invites the student to figure out how to solve the problem.

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This module addresses the real problem of determining the density of the Earth and invites the student to figure out how to solve the problem.

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After going over the concept of moment of inertia in class, students are asked to calculate density models of the earth. Three models of increasing complexity are developed, using additional constraints from seismology on the radius of the core. This homework assignment is typically the only assignment for the week - it gives the students practice in applying concepts and methods from physics and mathematics that usually have only been encountered in a theoretical fashion by the students. How we determine mass and moment of inertia are discussed in class. Usually students work together in small groups, as those whose math skills are rusty find this assignment difficult on their own. This activity uses geophysics to solve problems in other fields.

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The goal of this pair of labs is for the students to learn to apply rock and fossil identification skills to determining rock formations, sedimentary depositional environments, age ranges, and, ultimately, to writing a geologic history of a sequence of rocks from Bryce, Zion, and Grand Canyons. During the first of the two labs, the students learn to make fossil and sedimentary structures identifications. They add these skills to their rock and mineral identification skills to make interpretations of the sedimentary environments along a generalized profile from terrestrial to offshore locations. During the second lab, they apply these skills to a sequence of rocks from the southwestern U.S. to interpret the environmental changes that have occurred over time. They also begin to learn how to use fossils to determine age ranges for these changing events. Once they put together all of their data, they construct a stratigraphic column and piece together a written narrative of the geologic history of the area. The students work in groups to collect their data and determine their stratigraphy. They write their geologic histories individually. The students learn how to apply their skills and knowledge to make interpretations and also learn how to support their determinations with data.

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This project involves a field trip to the Jordan Formation in Winona, MN. Student teams are assigned a section of the outcrop from which they are to determine a stratigraphic column. The class then performs a lateral analysis and builds a composite stratigraphic column for the formation. As a final product, the students write up the class's observations about the formation.

Project Webpages

Project Summary and Write-up Outline (Acrobat (PDF) PRIVATE FILE 115kB Jul7 05)
Instructor Notes for Project (Acrobat (PDF) PRIVATE FILE 91kB Jul7 05)
Outlines and Notes (Acrobat (PDF) PRIVATE FILE 1.1MB Jul7 05) for each class session for this project

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In this activity, students confront several different models - from the DNA helix Watson and Crick constructed in their laboratory to a map of McDonalds density in the US - and work in small groups to derive their commonalities.

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This exercise begins with a demonstration of fluid flow through porous sediment using a constant head permeameter, with the students conducting the experiment and collecting the data. The demo is followed by a Think-Pair-Share exercise in which the question is posed to the class: "What could we change in order to increase flow through the system?" The class then works through their brainstormed list of ideas, discussing each and evaluating whether it is correct or a misconception. The students derive Darcy's Law qualitatively, based upon the results of the Think-Pair-Share exercise and discussions.

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Students prepare for this activity by working with a unidirectional flume with a sand bed. We adjust water depth, flow velocity, and channel slope to achieve a range of bed states, in an effort for them to understand the controls on bedforms. This portion of the activity could be done in lecture or via another exercise that makes use of digital video of actual experiments. The activity itself is a jigsaw: students form groups of three, each group responsible for plotting depth vs. velocity plots of bedform state for a single sand grain size range (0.10-0.14 mm, 0.5-0.64 mm, and 1.3-1.8 mm). These data are provided to them as Excel files and the data were directly 'stolen' from the original depth vs. velocity plots in Middleton and Southard (1984), Mechanics of Sediment Movement, SEPM Short Course Number 3. Datathief software (available free on the web) was used to steal the data. The data are arranged in columns: depth, velocity, and bedform type. Students must plot each of the different bedform types with a different symbol, then they have to define field boundaries. It is critical that they have never seen the original plots in their textbook. The goal is for them to derive them on their own, not to regurgitate what is in their textbook or elsewhere. After they complete their plots for each grain size range, the groups re-arrange themselves into groups of three with one representative from each of the grain size groups. They then must try to evaluate the effects of changing grain size on bedform state. Finally, after completing the exercise, the bedform analysis is linked to the cross stratification that is produced under conditions of high sediment fallout rates and the given bed state. The activity gives students practice working with realistic datasets, exposure to the role of physical modeling in sedimentary geology, and a chance to plot and interpret real data. Furthermore, it really solidifies the link between cross stratification and its dynamic interpretation from the rock record.

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In class, have students make a simple sketch of an outcrop shown in a slide (or computer projection) then discuss possible interpretations.

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Students are given a description of a fossil brachiopod, from the literature, along with a one-page handout describing the basic morphology of brachiopods. Students work independently to make a scale drawing of the fossil described (brachial valve, pedicle valve, anterior view, lateral view). They have access to textbooks (Moore, Laliker & Fisher; Clarkson), the Treatise volume, and the internet to get information on morphological terms. This takes about an hour, after which I display all of the diagrams on the wall along with the photographs from the paper from which the description was extracted. We discuss some of the differences and where problems arose in interpreting the description. I emphasize the importance of an accurate drawing or photograph to accompany a description.

Students are then given a different brachiopod specimen and asked to produce a written description (pedicle-valve, brachial valve, anterior view, lateral view) of their fossil similar to the one that they read--i.e. using all of the appropriate terms. They are told that other students will be trying to match their description to their specimen. I collect all of the descriptions, edit them (remove portions that use incorrect terminology or inappropriate), and produce a handout of all of the descriptions.

At the next class, students are given the descriptions and asked to match descriptions to specimens. They do this independently outside of class. The specimens are made available in the lab room for several days. I add a couple of 'extra' specimens (without description) so that it is not a process of elimination.

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