Which statement best explains why obsidian has a smooth glassy surface but basalt has a rough surface? Obsidian is formed due to
compaction and basalt is formed due to weathering. Obsidian allows less crystal growth than basalt because it cools more rapidly than basalt. Basalt is more easily eroded than obsidian because it is formed at a lower temperature than obsidian. Basalt is formed from the erosion of sediments and obsidian is formed due to the metamorphosis of rocks.
Obsidian allows less crystal growth than basalt because it cools more rapidly than basalt.
Explanation:
Both Obsidian and Basalts are igneous rocks. Igneous rocks from the solidification and cooling of magma.
The textures of igneous rocks relies mostly on their mode of formation. Igneous texture refers to the way minerals are formed and arranged in rocks.
When magma forms and cools rapidly, crystals of minerals don't have time to grow. This leads to the formation of a rock that would look like glass. An example of such rock is Obisdian. Obsidian's glassy and smooth texture is as a result of the way it was formed. This rock type is an extrusive igneous rock that forms on the surface where cooling magma solidifies rapidly and crystals have little to no time to solidify.
Basalt on the other hand is an extrusive igneous rock. The mineral grains here have some ample time to form. Basalt is made of mafic minerals which impacts some very interesting textures on the rock mass. The texture of a typical basalt is fine grained and the minerals can be seen when magnified. Cooling is not as rapid during the formation of basalts compared to obsidian.
