Geology
90 flashcards by MentisLibrary
Read the story written in rock, from the rock cycle and mineral properties to plate tectonics, earthquakes, and volcanoes. Includes how geologists date the past and reconstruct billions of years of Earth history.
- What are the three main rock types?
- Igneous, sedimentary, and metamorphic
- How does igneous rock form?
- By the cooling and crystallization of molten rock
- How does sedimentary rock form?
- By the compaction and cementation of sediment, or by chemical or biological precipitation
- How does metamorphic rock form?
- When existing rock is altered in the solid state by heat, pressure, or chemically active fluids
- What is the difference between magma and lava?
- Magma is molten rock beneath the surface; lava is molten rock that has erupted
- Why does intrusive igneous rock have larger crystals than extrusive rock?
- Slower cooling underground gives crystals more time to grow
- What is Bowen's reaction series?
- The order in which minerals crystallize from cooling magma
- What distinguishes felsic from mafic igneous rock?
- Felsic rock is silica-rich, light-colored, and lower density; mafic is iron and magnesium rich, dark, and denser
- What are clastic sedimentary rocks classified by?
- The size of their particles
- What is limestone made of and how does it form?
- Calcium carbonate, formed from shell and coral debris or by chemical precipitation
- What is a sedimentary facies?
- The set of characteristics of a sedimentary rock that reflects its depositional environment
- What does good sorting in a sediment indicate?
- Prolonged transport by a consistent-energy process such as wind or waves
- What is the difference between foliated and non-foliated metamorphic rock?
- Foliated rock has visible mineral banding or layering from directed pressure; non-foliated does not
- What does limestone become when metamorphosed?
- Marble
- What does sandstone become when metamorphosed?
- Quartzite
- What is contact metamorphism?
- Alteration of rock by heat from a nearby igneous intrusion
- What is regional metamorphism?
- Large-scale alteration by heat and directed pressure, typically during mountain building
- What is a mineral, by definition?
- A naturally occurring, inorganic solid with a definite chemical composition and an ordered crystal structure
- What is the most abundant mineral group in Earth's crust?
- The silicates
- What is the basic building block of all silicate minerals?
- The silica tetrahedron, one silicon atom surrounded by four oxygen atoms
- What does the Mohs scale measure and what are its endpoints?
- Relative scratch hardness, from talc at 1 to diamond at 10
- What is streak and why is it more reliable than color?
- The color of a mineral's powder on an unglazed porcelain plate, which is consistent even when surface color varies
- What is cleavage in a mineral?
- The tendency to break along planes of weak bonding, producing flat surfaces
- What is luster?
- The way light reflects off a mineral surface, described as metallic or nonmetallic
- What are the four main compositional layers of Earth?
- Crust, mantle, outer core, and inner core
- What is the difference between the lithosphere and the asthenosphere?
- The lithosphere is the rigid outer shell of crust and uppermost mantle; the asthenosphere below it is weak and flows slowly
- What is the Mohorovicic discontinuity?
- The boundary between crust and mantle, detected by a jump in seismic wave speed
- How does oceanic crust differ from continental crust?
- Oceanic crust is thinner, denser, basaltic, and young; continental crust is thicker, less dense, granitic, and old
- Who proposed continental drift and why was it rejected at first?
- Alfred Wegener in 1912, because he could not explain what force moved the continents
- What evidence supported continental drift?
- Matching coastlines, matching fossils across oceans, matching mountain belts, and ancient glacial deposits in now-tropical areas