Pumice? EarthCache

As you walk along the shoreline of the beach at the coordinates you can find pumice stones. These pumice stones can also be found on several beaches around Bahrain. These stones has been washed up and gathered here, so you are more likely to find them on the tide line.

Pumice is an igneous volcanic rock that consists of highly vesicular rough textured volcanic glass, It is usually a light colour. Itis created when heated,  pressurized molten rock is rapidly ejected from a volcano. The unusual foamy structure of pumice happens because of rapid cooling of the rock, allowing the dissolved gases inside to boil out and get trapped in the rock matrix. Pumice has an average porosity of 90%, giving it a density below 1.00 g/cm³ so it floats on water, until the pumice bubbles fill with water.

Pumice is widely used to make lightweight concrete or insulative low-density breeze blocks. This use can often be seen in the building debris around Bahrain. With no obvious source of Bahrain’s pumice nearby, it is possible that the pumice that you find here is from the building industry. When used as an additive for cement, a fine-grained version of pumice called pozzolan is mixed with lime to form a light-weight, plaster-like concrete. This form of concrete was used as far back as Roman times.

It is also used as an abrasive, especially in polishes, pencil erasers, cosmetic exfoliants. Pumice stones are often used in beauty salons during the pedicure process to remove dry and excess skin from the bottom of the foot as well as calluses. Finely ground pumice is added to some toothpastes and heavy-duty hand cleaners (such as Lava soap) as a mild abrasive.

In order to determine the density of a pumice rock you will need:

A measuring jug of at least 1 litre or more

A set of kitchen scales

A source of freshwater, not sea water.

A piece of pumice stone, which you should be able to find on the beach. Try and get it to be small enough to fit in the measuring jug.

Perform the following experiment on the pumice rock sample you find. You can do this on the beach if you take the equipment with you, or take your piece of pumice back home with you.

First, weigh the pumice on the kitchen scales, in grams

Fill the measuring jug with water to half way, this is amount A.

Use your finger, completely submerge the pumice rock in the water.

Note down the new water level this is amount B.

The volume of the pumice is A-B in cm³

The Density in g/cm³ of the pumice is Mass divided by Volume.

To log this Earthcache, you will NOT be looking for a typical geocache container (in fact, there is no container to find). Rather, to prove you were here and learned something you'll need to find the answers to the given questions.

Send your answers to the questions below to me, including the name of this earthcache. Feel free to log your find straightaway, I will contact you if there is a problem.

Alternatively, pumice can be found in other areas of Bahrain on the beaches. should you find pumice in another location, feel free to log this cache but let everyone know where the pumice site was, you still need to do the tasks set above.

1. Briefly, in your own words, describe how pumice is formed?

2. Using the method given in the description, what was the density of your pumice?

3. What were the exact coordinates of the place where you found your pumice?

4. Where do you think the pumice you found originated from?

5. Optional, it would be great if you included a picture of yourself at gz.

   

   I am a proud