Table of Contents
How fast do porphyritic rocks cool?
Porphyritic:a mixture of large and small crystals – perhaps a two-stage cooling history with the large crystals (the phenocrysts) cooling slowly and the small crystals (the groundmass) cooling more quickly.
What is the cooling history of porphyritic texture?
A porphyritic texture is developed when magma that has been slowly cooling and crystallising within the Earth’s crust is suddenly erupted at the surface, causing the remaining uncrystallised magma to cool rapidly. This texture is characteristic of most volcanic rocks.
What does the porphyritic texture indicate about the cooling rate of magma?
What does a porphyritic texture indicate about the cooling history of an igneous rock? It indicates that crystals were formed at depth (slow cooling) and then the magma moved to a shallow depth or erupted (fast cooling).
How do you determine the cooling rate of igneous rocks?
The appearance of the rock is created by the composition of the magma. It is also determined by the rate that the magma cools. If the magma cools deep underground, it cools slowly. If the magma cools at or very near the surface, it cools quickly.
What is the cooling rate of peridotite?
Published studies demonstrate cooling rates for the Iwanaidake peridotites to be on the order of 10−4–10−1 °C/yr, while, for extrusive rocks such as picrites, cooling rates are estimated at 103 to 104 °C/yr [9].
What is the cooling rate of Obsidian?
It’s about 1,000 degrees Celsius (1,830 degrees Fahrenheit). That’s about five times as hot as your oven when you bake a cake! Rondi: Sounds like what scientists call a “volatile situation.” Obsidian: If there’s any crack or weak zone above the magma chamber, that magma is going to blow!
How cooling rate affect the formation of igneous rock?
The texture of an igneous rock (fine-grained vs coarse-grained) is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals. They cool too quickly to form crystals.
Are porphyritic rocks intermediate?
Cooling of the magma can occur deep beneath the surface (plutonic), beneath the surface but at relatively shallow depths (hypabyssal) or on the surface (volcanic)….Igneous Rocks.
| Atlas of Igneous Rocks | Rock Name / Image | Andesite: Hornblende Andesite |
|---|---|---|
| Texture | Porphyritic | |
| Composition | Intermediate | |
| Occurance | Volcanic | |
| Images | Close-up |
What is the cooling rate of basalt?
These calculations have provided the fastest cooling rate (105.31 K s−1 for the finest limu o Pele fragments) measured in natural volcanic glass to date.
Is Basalt fast or slow cooling?
Basalt is extrusive. The magma from which it cools breaks through the crust of the earth and erupts on the surface. Because the magma comes out of the earth (and often into water) it cools very quickly, and the minerals have very little opportunity to grow.
What kind of rock is a porphyritic rock?
Porphyritic Rock. Porphyritic rock is igneous rock which is characterized by large crystals surrounded by a background of material with very small crystals.
What is the texture of a pyroclastic rock?
The material may range from fine dust or fine hair-like strands to large molten blobs. The consolidation of such material into rocks produces what is called the pyroclastic texture. Classification by texture Index Igneous rock concepts
What makes a phaneritic rock an intrusive rock?
Phaneritic rock is igneous rock with large, identifiable crystals of roughly equal size. Such crystals are characteristic of rocks which solidified far below the surface so that the cooling was slow enough to enable the large crystals to grow. Such rocks are termed “intrusive” rocks.
What kind of rock has an aphanitic texture?
Such rocks are termed ” extrusive ” rocks. Under these conditions, there is not enough time for the growth of large crystals. Basalt from surface lava flow often exhibits an aphanitic texture.