Question

15)What is the difference between a dike, a sill, a laccolith and a batholith? 16) Which two intrude with the layers (concordant)? 17) Which two are discordant (intrude through layers)? 18) Which is the largest of the four? 19) What is obsidian and how does it form? Is it a rock or a mineral? Explain. 20) What is a vesicle? Does it form in igneous intrusive or extrusive igneous rock? Why does it form ? 21) What is a pyroclastic texture and how does it form? 22) Pyroclastic-Aphanitic-Phaneritic- Glassy. Which of the 4 textures would be in igneous intrusive rocks? 23) Identify rocks with an aphanitic texture (two rocks) and a phaneritic texture (three rocks) . Which are intrusive? Which are extrusive? Which cooled slowly? Which cooled quickly? 24) What are xenoliths? Draw a picture of xenoliths in a rock on the whiteboard and label the rock names and sources of two rocks. 25) What is assimilation and how does it relate to xenoliths? What happens to magma composition in assimilation? 26) What is the difference between a crater and caldera? 27) What is the difference between lahar and a pyroclastic flow? 28) Which volcano is made primarily of pyroclastics? 29) What volcano is made of a combination of lava and pyroclastics? Give three examples of this volcano type. 30) What is the difference between the discontinuous and the continuous path in Bowens Reaction series? 31) Which mineral crystallizes first in Bowens? Which is last? Which is the higher temperature mineral? 32) What volcano is made of low viscosity magma /lava? What is an example of the rock that forms in this volcano? What is an example of this type of volcano? 33) The geothermal gradient is __________/kilometer. 34) What is the geothermal gradient? 35) What is the source of dark colored igneous rocks? 36) Name the conditions in earth that cause rock to melt?

Answer 1

15)Dike is a vertical cross cutting igneous intrusion which intersects the overlying formation.

Sill is a igneous intrusion which remains parallel to formation.

Laccolith is a sheet like intrusion in a sedimentary formation which uplifts overlying structures like domal uplift.

Batholith is a large intrusive body forms due to cooling of magma from magma chamber. It is usually granitic in composition.

16)Sills and laccolith are concordant.

17)Dike and batholith are discordant.

18)Batholith is largest among four .

19)Obsidian is extrusive felsic glassy igneous rock.They formed due to rapid cooling of magma when they come to surface exposure directly.

It is a mineral.

20)A vesicles is one type of cavity usually formed basalt formed by rapid quenching of magma.

It is extrusive rock,formed by rapid cooling of magma .

It formed vesicles due to presence of volatile enrichment.

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