Associate Level Material

Comparison Worksheet

Use the following table to compare extrusive and intrusive rocks. Describe and compare each type in at least 150 words.

Extrusive Rock Intrusive Rock
Extrusive igneous rocks are formed at the crust's surface as a result of the partial melting of rocks within the mantle and crust. Extrusive Igneous rocks cool and solidify quicker than intrusive igneous rocks. When lava is exposed to the atmosphere or water outside of the earth, this causes the lava to cool very rapidly in comparison to intrusive rocks. This rapid cooling does not allow the rock time to form large crystals in the way that intrusive rocks do. Extrusive rocks have a fine-grained texture known to geologists as aphanitic, because the mineral crystals present within the rock are very small. It is much more difficult to distinguish between the different types of extrusive igneous rocks than between different types of intrusive igneous rocks because the minerals are mostly fine-grained. Examples of extrusive igneous rocks are basalt and obsidian. Rhyolite is the extrusive counterpart of granite due to its high silica concentration, but fine-grained texture. One form of igneous rocks, intrusive rocks, derives directly from magma and solidifies within the earth. Since intrusive rocks are within the earth, they cool very slowly, taking anywhere from thousands to millions of years to cool enough to completely solidify. The cooling rate of intrusive rocks enables the crystals to form that are visible to the naked eye, which gives them a coarse grain compared to extrusive rocks. This visible grain is called a phaneritic texture. Intrusive rocks can also be classified according to the shape and size of the intrusive body and its relation to the other formations into which it intrudes. Typical intrusive formations are batholiths, stocks, laccoliths, sills and dikes. Granite is one example of an intrusive igneous rock. It contains a high concentration of silica in the form of its quartz crystals. The central cores of major mountain ranges consist of intrusive igneous rocks. When exposed by erosion, these cores may occupy huge areas of the Earth's surface.

Use the following table to compare faults and folds. Describe and compare each feature in at least 150 words.

Faults Folds
A fault is a crack in the Earth's crust. Typically, faults are associated with, or form, the boundaries between Earth's tectonic plates. In an active fault, the pieces of the Earth's crust along a fault move over time. The moving rocks can cause earthquakes. Inactive faults had movement along them at one time, but no longer move. The type of motion along a fault depends on the type of fault. The main types of faults are normal dip-slip faults, reverse dip-slip faults, and transform (strike-slip) faults. Often movement along a fault is not entirely of one variety. A fault may be some combination of strike slip and normal or reverse faulting. To further complicate these conditions, faults are often not just one orderly break in the rock, but are instead a number of fractures caused by similar motions of the Earth's crust. These clusters of faults are called fault zones. The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur singly as isolated folds and in extensive fold trains of different sizes, on a variety of scales. Folds form under varied conditions of stress, hydrostatic pressure, pore pressure, and temperature. A set of folds distributed on a regional scale constitutes a fold belt, a common feature of orogenic zones. Folds are commonly formed by shortening of existing layers, but may also be formed as a result of displacement on a non-planar fault, at the tip of a propagating fault, by differential compaction or due to the effects of a high-level igneous intrusion.

Use the following table to identify extrusive and intrusive rocks with pictures. Pick at least two intrusive rocks and two extrusive rocks, and paste a picture of each rock into the Picture column. For each rock, describe the physical characteristics and write a 50- to 100-word explanation about how the characteristics prove whether it is an extrusive or intrusive rock.

Picture Physical Characteristics Intrusive or Extrusive? Smooth, glossy, shiny, black, with a fractured type of break. This rock is extrusive because the smooth glassy texture indicates that this rock probably goes through a very fast cooling process. Also there are no indications of visible crystals that have form on this rock. I found out this particular rock is sometimes classified as a mineraloid instead of a mineral, because its composition is too complex to comprise a single mineral. Rough, coarse-grained, and dark-colored. I believe this rock is intrusive because there are visible crystals throughout the rock. Crystals in intrusive rocks can be seen by the naked eye, while crystals in most extrusive igneous rocks are not easily visible.
Based on this theory alone I would definitely say that this is an intrusive rock. Rough, coarse-grained, white with gray and black mixed in. There are also visible crystals on this type of rock (much like the previous rock identified). That is the main reason I believe this rock is intrusive. I have learned that this rock is much like granite because some contain ten percent quartz. If you have more than ten percent quartz, would probably be granite. Smooth look, light-colored, and fine-grained. I would say that this rock is extrusive. For one, it has a smooth fined-grained look and that could signify that it cools very quickly. I would also say it is extrusive because from what I see it has no visible crystals. I found out that this rock typically contains quartz and feldspar minerals.

In 100 to 200 words, suggest how the game in the museum might work.

The in the museum would work by giving the participants a sheet of paper that explains the difference between extrusive and intrusive rocks. Then the participants would receive a sheet of paper asking them to find the physical characteristics in order to identify each rock in the exhibit. The participants would then go around the exhibit and examine by touching and observing each rock. By knowing the difference between extrusive and intrusive rocks the participants should be able to figure out which rock belongs to each class. The person with the most correct answers on the quiz would win a prize.