Friday, October 12, 2012

Metamorphic Rocks & The Rock Cycle

We finished up our Rock and Mineral study!!

Metamorphic rocks are formed when other rocks – which could be igneous, sedimentary or metamorphic – are exposed to heat and pressure, changing them into different rocks.   I read the description of metamorphic rocks from our RSO to the kids and we discussed how these were different from igneous and sedimentary rocks.

We took a close up look at our three rocks and used the identification key to decide what they were.

IMG_1043 IMG_1044

Marble (13 – above) is made from the metamorphism of sedimentary carbonate rocks – limestone and dolomite.  It is nonfoliated, which means it does not form layers.

Slate (14 – above) is made when shale is metamorphosed.   It has very tiny particles, and an even appearance although the color can vary.  Usually it will be dark gray or black but it can be greenish, reddish or brownish.  Our outside patio is made with slate in a variety of colors so the kids are used to seeing it.  Slate is foliated (layered) allowing it to be split into flat pieces, which are used for roof tiles, chalkboards and stepping stones.

Schist (15 – above) is formed in visible layers – foliated – with large crystals that are formed due to high heat.    It can have many different looks depending on what minerals are found in it.

After we were able to identify our three rocks, we made cookies to demonstrate how rocks are formed.  We divided sugar cookie dough into three separate bowls, and colored each one a different color.   The main comment at this point was “GROSS!” and I can’t say I disagreed.


We took a little bit from each color (each “mineral”) and formed them into rocks.


I asked the kids what they thought was going to happen when we baked them.  Georgie thought they would melt completely and we would have brown cookies.  Vicki thought they would only melt a little bit and we would have multi-colored cookies.   And, of course, the winner was…….


everyone in the house who likes sugar cookies. ;-)

After we finished our discussion of Metamorphic rocks, we discussed the Rock Cycle. We pulled out all nine of the rocks from our RSO rock and mineral kit and used a diagram of the rock cycle to place them in the correct places.  I did refer back to the identification pages from each of our previous units to help us with this.  Georgie remembered right away that obsidian and granite were igneous and that the "sandy" one was sedimentary. 

Georgie then played the Level 2 Rock Cycle game at The Learning Zone from the Oxford Museum of Natural History

Since he was able to complete the game without any problems, it appears he actually learned something from our study.

We will now be taking a short break from science to start our US Geography and US History studies.

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