Question

understand concepts

1. what is a rock?
2. which igneous rock forms when basaltic lava hardens? when basaltic magma hardens?
3. a rock has a porphyritic texture. what can you conclude about the rock?
4. how are granite and rhyolite the same, and how do they differ?
5. explain the two main types of weathering.
6. why is most of earths solid surface composed of sediments or sedimentary rocks?
7. distinguish between regional and contact metamorphism.
8. what is the difference between shale and slate?

use the following diagram to answer questions 19 - 22.

1. what process occurs at point a?
2. what three processes can occur at point b?
3. name two processes that occur at point c.
4. what two processes occur at points d and e?

Explanation:

1. A rock is a solid, cohesive aggregate of one or more minerals or mineral - like matter.
2. Basalt forms when basaltic lava hardens. Andesite forms when basaltic magma hardens beneath the surface.
3. A rock with porphyritic texture has large crystals (phenocrysts) embedded in a fine - grained matrix, indicating two stages of cooling (slow then fast).
4. Granite and rhyolite are both felsic igneous rocks with similar chemical composition. Granite is intrusive (coarse - grained) and rhyolite is extrusive (fine - grained).
5. The two main types of weathering are physical (mechanical) weathering which breaks rocks into smaller pieces without changing their chemical composition, and chemical weathering which changes the chemical makeup of rocks through processes like oxidation and dissolution.
6. Most of Earth's solid surface is composed of sediments or sedimentary rocks because weathering and erosion break down pre - existing rocks into sediments, which are then transported and deposited, and over time lithified into sedimentary rocks.
7. Regional metamorphism occurs over large areas due to high pressure and temperature associated with tectonic activity. Contact metamorphism occurs around an igneous intrusion due to heat from the magma.
8. Shale is a fine - grained sedimentary rock composed of clay minerals. Slate is a low - grade metamorphic rock formed from shale, which is more compact and has a foliated texture.
9. At point A, the process is cooling and solidification (crystallization) of magma to form igneous rocks.
10. At point B, the three processes are weathering, erosion, and transportation of igneous rocks to form sediments.
11. At point C, the two processes are compaction and cementation of sediments to form sedimentary rocks.
12. At points D and E, the two processes are metamorphism (recrystallization under high pressure and/or temperature) of sedimentary and igneous rocks respectively to form metamorphic rocks.

Answer:

1. A solid, cohesive aggregate of one or more minerals or mineral - like matter.
2. Basalt (from lava); Andesite (from magma).
3. Has large crystals in a fine - grained matrix, two - stage cooling.
4. Similar: Felsic, similar chemistry; Different: Granite is intrusive (coarse - grained), rhyolite is extrusive (fine - grained).
5. Physical (mechanical): Breaks rocks without chemical change; Chemical: Changes chemical makeup.
6. Weathering and erosion form sediments, which lithify into sedimentary rocks.
7. Regional: Large - scale, tectonic; Contact: Around igneous intrusion, heat - based.
8. Shale: Sedimentary, clay - based; Slate: Metamorphic, foliated.
9. Cooling and solidification (crystallization).
10. Weathering, erosion, transportation.
11. Compaction, cementation.
12. Metamorphism.