A brief geology lesson from one of many excellent displays in The National Museum of Malaysia (Museum Negara).
Brad and Janet were lucky enough to find some very interesting ECs whilst visiting Malaysia, aided by some kind assistance from some local of the local COs.
We decided we would try to create another local EC as a small acknowledgement of this and to contribute to the growing local EC collection.
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Types of Rocks:
The three main types of rock are Sedimentary, Metamorphic, and Igneous. The differences between them have to do with how they are originally formed.
Sedimentary Rocks:
Sedimentary rocks are formed by the lithification (cementing, compacting, and hardening) of existing rock and/or the bones, shells, and pieces of formerly living animals and plants. Rocks are weathered and eroded into tiny particles which are then transported usually by wind and water and deposited along with other pieces of rock called sediments.
Sediments usually sort themselves by the size of the particles during the deposition process so sedimentary rocks tend to contain similarly sized sedimentary particles. Over a long period of time the sediment accumulates in layers and are cemented, compacted, and hardened over time by the weight and pressure of up to thousands of feet of additional sediments above them. This turns the sediments into rock. Sedimentary rock is usually fairly soft and may break apart or crumble easily. You may see sand, pebbles, or stones in the rock. Because of the way it forms, it is usually the only type that contains fossils which are formed from the dead animal and plant parts which may be mixed into the layers before they solidify. A common example of this rock type is limestone.
Metamorphic Rocks:
Metamorphic rocks are usually created when they come under extreme pressure such as under many thousands of feet of bedrock or through being crushed at the junction of tectonic plates. Sedimentary rocks can become metamorphic rocks if the thousands of feet of sediments above them apply enough heat and pressure to further change the structure of the sedimentary rock. The heat and pressure comes from inside the earth. From the upper mantle up to within a few kilometers of the surface of the earth there is a tremendous amount of heat and pressure. This heat and pressure increase with depth. The rocks that result from these processes often have ribbonlike layers and may have shiny crystals, formed by minerals growing slowly over time, on their surface. Metamorphic rocks are harder than other types of rock so they're more resistant to weathering and erosion. A common example of this rock type is marble.
Igneous Rocks:
Igneous rocks are formed when magma cools and hardens. Sometimes the magma cools inside the earth, and other times it erupts onto the surface from volcanoes producing lava. When lava cools quickly no crystals form and the rock looks shiny and almost glasslike. However sometimes gas bubbles are trapped in the rock during the cooling process, leaving tiny holes and spaces in the rock. A common example of this rock type is basalt.
These images show some of the key characteristics of these three types of rocks.
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Crystals
Small, flat surfaces that are shiny or sparkly. |
Fossils
Imprints of leaves, shells, insects, or other items. |
Gas bubbles
Holes like Swiss cheese. |
Glassy surface
A shiny and smooth surface. |
Ribbonlike layers
Straight/wavy stripes of different colors. |
Sand or pebbles
Individual stones, pebbles, or sand grains visible. |
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The Rock Cycle:
All three rock types can be turned to any other rock type via the Rock Cycle. Sedimentary to Igneous or to Metamorphic, Metamorphic to Sedimentary or Igneous, and Igneous to Sedimentary or metamorphic. This image shows depicts the cycle.
Claiming this EarthCache:
The posted coordinates will take you to the entrance to the National Museum of Malaysia. If you require wheelchair access the related webpage indicates that it is available and provides detail about the Museum.
From KL Sentral, you can walk to Museum Negara (the National Museum) via the walkway to Museum Negara MRT station which is located just in front of the museum.
There is an entry fee. At the time of publication of this cache admission cost RM2 for locals and RM5 for foreigners.
Once inside turn to right and enter Exhibition Hall A. Immediately inside that doorway turn to your left and you will find the "Rocks in Malaysia" Exhibit. This provides information about the geological history in Malaysia and contains a number of examples of different rock types.
To claim this Earthcache please email CO the answers to these 3 questions. The answers to Q2 and Q3 are available from the exhibit.
- Question 1: Please explain how the rock cycle stages work for a rock to go through each the three changes from Magma to Igneous to Metamorphic to Sedimentary.
- Question 2: Where and when did the sedimentation begin to form the oldest rocks in Malaysia?
- Question 3: What are the four rock types named on the labels in the fourth display case from the left.
- (Optional) Feel free to post an image of yourself or your GPSr at the museum but no spoiler images please. In accordance with GC rules there is no requirement for this.
If you have time please explore the rest of this very interesting Museum.