Igneous Rock
Rock formed from the cooling and solidification of magma or lava.
igneous rock
Small pieces of rock, mineral grains, or organic material produced by weathering and erosion.
sediments
Who is a sedimentologist?
A geologist who studies sediments, sedimentary rocks, and the processes that create them.
What is lithification?
The process that turns sediments into solid sedimentary rock.
BONUS QUESTIONS ABOUT MINERALS
Fluorescence: Glows only while exposed to UV light.
Phosphorescence: Continues to glow after the UV light source is removed.
Which has higher melting points — felsic or mafic?
Mafic rocks have higher melting points.
Three groups of sedimentary rock
Clastic, chemical, and carbonate (or organic).
Why does pumice float?
It contains many air-filled vesicles that make it less dense than water.
Compaction
Sediments are pressed together under weight, reducing pore space.
Four characteristics of minerals
Naturally occurring, inorganic, solid, and has a definite chemical composition and crystal structure.
Four groups by texture
Fine-grained, coarse-grained, porphyritic, and glassy.
How is clastic rock formed?
From compacted or cemented fragments of pre-existing rocks.
Who was Florence Bascom?
A pioneering American geologist and the first woman hired by the U.S. Geological Survey; known for her work on petrography and crystalline rocks.
Cementation
Minerals precipitate between sediment grains and “glue” them together.
How many levels are there in the Mohs Hardness Scale?
10 levels
Difference between extrusive and intrusive rock
Extrusive rocks form from lava on the surface and cool quickly; intrusive rocks form from magma underground and cool slowly.
How is chemical rock formed?
From minerals precipitating or crystallizing out of a solution (because of water evaporation).
What is intermediate rock?
Igneous rock with moderate silica content, between mafic and felsic (e.g., andesite, diorite).
Erosion
The movement of sediments by wind, water, ice, or gravity.
Why is the field hardness scale called “field”?
Because it uses easily accessible objects (like a fingernail, penny, or steel) to test hardness in the field without lab equipment.
Difference between magma and lava
Magma is molten rock beneath Earth’s surface; lava is molten rock that has erupted onto the surface.
How is carbonate rock formed?
Mainly from the accumulation of carbonate minerals such as calcite, often from shells or marine organisms (organic)
Difference between all 4 textures of igneous rock
Fine-grained: small crystals from fast cooling.
Coarse-grained: large crystals from slow cooling.
Glassy: no crystals; extremely rapid cooling.
Porphyritic: large crystals embedded in a fine-grained matrix; two-stage cooling.
Stratification
The formation of sedimentary layers (strata).
What causes natural nuclear radiation in minerals?
The presence of unstable radioactive elements or isotopes such as uranium, thorium, or potassium-40.