Geology Exam 2 Review

What are some of the main physical properties used to identify minerals?

hardness (resistance to scratching), color, luster (how light reflects), streak (color of the mineral powder), cleavage and fracture (how a mineral breaks), crystal habit (external shape), and specific gravity (density)

How are some physical properties related to chemical bonding and element composition?

List known mineral properties. Which mineral properties are the most reliable (you find the same result each time you perform the test on this mineral).

hardness and streak

The gray, black, brown varieties of quartz, known as ‘Smoky quartz’ is caused by: A) Ash particles trapped inside; B) Gamma radiation and trace Al; C) Baking quartz in the oven.

gamma radiation and trace AI

What are the three components of magmas?

liquid, solid, gaseous

How can we identify if a rock is plutonic (cooled underground aka intrusive) or volcanic (erupted at the surface of the Earth aka extrusive)?

examine its texture, particularly the size of its mineral crystals

What are some controls on whether a volcanic eruption will be explosive or effusive?

viscosity and gas content, as well as the ease of gas escape from the magma

What types of rocks are commonly formed at mid-ocean ridges, rifts, subduction zones, and hotspots?

basalt and grabbo

What are the different processes to melt the mantle?

decompression melting (lowering pressure as mantle rises), flux melting (adding water that lowers the melting point), and heat-induced melting (increasing temperature, often by a mantle plume)

What is the difference between a mafic and felsic magmas/rock? What is an intermediate magma/rock?

Mafic magma/rocks are rich in magnesium (Mg), iron (Fe), and calcium (Ca), low in silica and denser, often appearing darker in color.

Felsic magma/rocks are higher in silica, potassium (K), sodium (Na), and aluminum (Al), are less dense, and are typically lighter in color.

Which minerals make up Bowen’s reaction series, and what does it tell us about the minerals we expect to find in mafic and felsic igneous rock types?

olivine, pyroxene, biotite, potassium feldspar, muscovite, and quartz as minerals that crystallize from cooling magma at specific temperatures, moving from high-temperature mafic minerals to low-temperature felsic minerals.

Which of the following igneous intrusions cuts across pre-existing rock layers? A) Sill; B) Dike; C) Pyroclastic Flow

dike

What is the name of this magma: it forms at high temperatures (~1000 degrees) and contains olivine, pyroxene, and Ca-rich plagioclase. A) Basalt; B) Andesite; C) Rhyolite.

basalt

What factors control magma viscosity and do you think magma viscosity stays constant during cooling and solidification?

silica content, temperature, and dissolved gases

What is the difference between weathering and erosion?

Weathering is the process of breaking down rock into smaller pieces at its original location, while erosion is the subsequent process of moving those smaller pieces (sediments) away from that location by agents like water, wind, and gravity

How do we lithify sediment into sedimentary rock?

lithification, a process involving compaction, where overlying sediments squeeze out water and pore spaces

What structures can we often preserve in sedimentary rocks that provide clues to the depositional environment?

cross-bedding, ripple marks, graded bedding, mud cracks, and sole marks

What are some of the common rock names in each category?

How can we tell if a limestone is biochemical or chemical in origin?

by looking for fossils; the presence of shells, coral, or other biological remains indicates a biochemical origin

How does grain size and mineral composition contribute to sediment maturity in clastic rocks?

reflecting the duration and intensity of the sediment transport and weathering process

What type of rock would we expect to find in: a) a mountain stream; b) a river; c) beach; d) the ocean floor?

a) Mountain stream: Sedimentary rocks like conglomerate or sandstone, b) River: Sedimentary rocks like siltstone, sandstone, or shale, c) Beach: Sedimentary rocks like sandstone or beachrock, d) Ocean floor: Basalt (igneous rock). 

Where do carbonates form, and where do evaporites form?

Where do carbonates form, and where do evaporites form?

Carbonates form primarily in warm, shallow marine environments like carbonate platforms and shelves due to the activity of organisms and chemical precipitation from supersaturated water, but also in non-marine settings such as lakes and hot springs. Evaporites form in restricted basins where water evaporation exceeds freshwater influx, leading to the precipitation of minerals like halite, gypsum, and carbonates. Key evaporite environments include salt marshes (sabkhas), playa lakes, and permanently restricted marine settings like the Dead Sea or Mediterranean Sea. 

Which sedimentary rock class does Mudstone belong to? A) Chemical; B) Biochemical; C) Clastic; D) Organic

clastic

On the image (see slide #29 for example), click on one environment where carbonate rocks can form.

Recall the definition of metamorphism, describing the ‘ingredients’ and processes that occur.

What characteristics of the rock change during metamorphism?

mineral composition, texture, and structure

How can we turn a protolith into a metamorphic rock? What actions could achieve this?

Compare reasons for the diversity of metamorphic rocks.

Name different rock types that can form at low, medium, and high metamorphic grade.

Are pressures and temperatures the same everywhere within the Earth?

No

Distinguish the rock types formed during regional metamorphism and contact metamorphism

Describe how a foliation forms in a metamorphic rock.

What did George Barrow discover in Scotland in the 1890’s?

the Barrovian series. These are also called metamorphic facies series. A metamorphic facies series is a sequence of metamorphic facies which plot in a temperature-pressure diagram along a line, and this line represents a certain geothermal gradient.

What type of metamorphic environment does a skarn, quartzite, or marble form in?

high temperature