Match each metamorphic rock with the correct parent rock. 1. quartzite limestone 2. marble sandstone
The Correct Answer and Explanation is:
Correct Answer:
- Quartzite — Sandstone
- Marble — Limestone
Explanation:
Metamorphic rocks are formed when existing rocks, called parent rocks, undergo changes due to high temperature, pressure, or chemically active fluids within the Earth. These processes do not melt the rock but transform it in texture, mineral structure, or chemical composition.
Let us examine the pairings one at a time:
1. Quartzite from Sandstone
Quartzite is a hard, non-foliated metamorphic rock that originates from sandstone. Sandstone is composed mainly of quartz grains that are cemented together. During metamorphism, intense heat and pressure cause these quartz grains to fuse together into a dense, hard rock with interlocking crystals. The transformation eliminates the pore spaces between grains, making quartzite much more resistant to weathering and erosion compared to its parent sandstone. Because both rocks are composed primarily of quartz, their chemical composition remains similar, but the structure and appearance change significantly.
2. Marble from Limestone
Marble is a metamorphic rock that forms when limestone is subjected to high temperatures and pressures. Limestone is mainly composed of calcite, a mineral made of calcium carbonate. During metamorphism, the calcite crystals in limestone grow larger and interlock to form marble. This process can also remove fossils and sedimentary layers that were present in the original limestone. As a result, marble becomes a more uniform and crystalline rock, often used in sculpture and architecture due to its beauty and ability to be polished.
These transformations demonstrate how parent rocks evolve under geological forces, forming new rock types with distinct physical and chemical characteristics. Identifying parent rocks helps geologists understand the geological history of a region and the processes that have shaped it over time.
