A LESSON PLAN ON THE GEOLOGY EXPERIMENT CARRIED OUT BY PORTUGAL

Compressive and Distensive Forces

Objective: Represent the way that compressive and distensive forces act in nature.

Introduction: Tectonic forces are those which cause movement of the lithosphere and alter its configuration. They are originated by the convection currents in the asthenosphere, which are the circulations of its material (lighter, warm material rises while heavier, cool material sinks). There are 3 types of tectonic forces: compressive (in which there is a pushing of rocks) (A), tensional (which cause stress on rocks, pulling them apart) (B), these 2 are the most common ones; however, there are also shearing forces (C).

These movements may create faults and folds. Faults are fractures that occur in brittle rocks; there are the normal faults (caused by distensile forces, leading to the lowering of the hanging wall) and reverse ones (caused by compressive stresses, leading to the rise of the hanging wall).

Folds occur when a ductile block bends or curves resulting in permanent deformation.

Activity A: Convection Currents

○ In this experiment, try to observe the convection currents in the Lava Lamp’s mechanism.

Activity B: Oceanic Crust Expansion

○ In this Experiment we have a model that explains how the oceanic crust expands and the age of the geologic blocks.

○ To explain this process, we are going to use labels to demonstrate the age of the blocks and the formation of newer layers near the rift.

Step 1: Place your hands on the blue straps;

Step 2: Move them apart at the same rate;

Step 3: Try and guess how old the spot A and B are after they

Activity C: Reverse and Normal Faults using Soap Bars

In this Experiment, we are going to use a bar of soap to represent the 2 types of faults, normal and reverse, and see how they work.

Materials:

○ 1 bar of soap

○ 4 wood sticks

○ Water

○ 1 tray

Step 1: Fill the tray with water and sink the bar of soap where the 2 parts meet to lubrificate.

Step 2: To represent reverse faults, compress the 2 wood sticks together so that the hanging wall rises, and the footwall remains.

Activity D: Tectonics/soil layer experiment model

In this experiment we pretend to demonstrate how the layers of sediments are disposed before and after convergent movements.

Materials:

○ Flour

○ Yellow Sugar

○ Tectodidac model

○ Powdered Chocolate

○ Breadcrumbs

Step 1: Put a good amount of flour inside the box and press it to smooth it out.

Step 2: Repeat the Step 1 with powdered chocolate, yellow sugar and breadcrumbs until you have the box half filled.

Step 3: Push one iron bar very slowly and watch how the layers act during convergent movements.