Which is made up of the largest particles?
A) conglomerate
B) limestone
C) sandstone
D) siltstone
E) shale
The Correct answer and Explanation is:
The correct answer is A) conglomerate.
Explanation:
Conglomerate is a type of sedimentary rock that is made up of the largest particles among the options listed. It typically consists of rounded clasts or fragments, which are usually larger than 2 millimeters in diameter, embedded in a finer-grained matrix of sand, silt, or clay. These clasts are often pebbles, cobbles, or even boulders, indicating that conglomerate forms in environments where high-energy processes, such as fast-flowing rivers or beaches with strong wave action, transport and deposit large sediment particles.
Comparison to Other Rocks:
- Limestone: Limestone is primarily composed of calcium carbonate, often in the form of the mineral calcite. It forms from the accumulation of marine organisms’ shells and skeletal fragments or through chemical precipitation in shallow seas. The particles in limestone are much finer compared to conglomerate, often microscopic or less than 1 millimeter in diameter.
- Sandstone: Sandstone consists mainly of sand-sized particles (0.0625 to 2 millimeters in diameter), typically quartz or feldspar. Although the grains in sandstone are visible to the naked eye, they are still much smaller than the pebbles and cobbles found in conglomerate.
- Siltstone: Siltstone is made up of particles in the silt-size range (0.0039 to 0.0625 millimeters in diameter). These particles are smaller than sand but larger than clay, giving the rock a smooth texture when rubbed.
- Shale: Shale is composed of very fine clay or mud particles, less than 0.0039 millimeters in diameter. It forms in quiet water environments, like deep ocean floors or lake bottoms, and has the smallest particles of the options given.
In summary, conglomerate contains the largest particles due to its formation in high-energy environments where large clasts are transported and deposited, distinguishing it from the finer-grained rocks like limestone, sandstone, siltstone, and shale.