Physical Geology Exam #2

What are Sedimentary Rocks?

Hard layers of Earth formed when small pieces of rock, minerals, and dead plants were pressed over time

What are the types of sedimentary rocks?

Clastic, chemical, Bio chemical

What is lithification?

The geological process that turns loose, unconsolidated sediment (such as sand, silt, mud, or gravel) into solid sedimentary rock

What is weathering?

The physical or chemical breakdown of rock with NO TRANSPORT

What is erosion?

Transport of weathered rock away from a location by active surface processes (wind, gravity, water, ice)

During the process of weathering, why would limestone weather significantly compared to sandstone?

Limestone has acid in it, which dissolves in acid

What is Hydrolysis?

Water partially dissolves the igneous silicate minerals, leaving behind clay minerals as residues

Clastic Sedimentary rocks

sedimentary rocks made from weathered sediments of other rocks adn deposited

Chemical Sedimentary rocks

rocks formed from minerals precipitated from a solution or left behind by evaporation

What is compaction?

The process that presses sediments together

What is cementation?

When the dissolved minerals crystallize and glue particles of sediment together

How are the textures of sedimentary rocks affected?

By the different energy processes that the rocks travel in

What would you need to do to get the smallest particles to deposit into the bed?

Adjusting the flow of the particles that are moving in

Explain how you can use the mineralogy of Arkose to determine that it formed close to the source of its sediments

Arkose contains K-Feldspar, which turns into clay when weathering because it does not survive long transport distances.

What occurs on a high-energy environment?

Landsliding

What's an example of a rock that comes from a high-energy environment, coarse, poorly sorted, and angular?

Breccia

What's a rock that also comes from a high-energy environment, poorly sorted, coarse, but rounded?

Conglomerate

What's a rock that comes from a low-energy environment and matures due to the heavier clasts being left behind?

Arkose

What's a rock that comes from a medium-high energy environment, sub-rounded to sub-angular since sand isn't moving constantly

Sandstone

What rock(s) comes from the continental shale and deep marine

Shale and Slitstone

What is the process of chemical sedimentary rocks?

Evaporite basins and salts

What are some chemical sedimentary rocks?

Limestone, Halite, Chert

Where does Limestone form?

Calcite becomes insoluble in water and crystallizes on the seafloor to form limestone on the continental shelf in tropical regions

What are the three ways that magma is made?

Divergent & Convergent plates, and Hot spots (mantle plumes)

What are Mantle Plumes?

Hot, less dense mantle material from the core-mantle boundary

Why do Mantle plumes rise?

They are hot and less dense than the surrounding mantle (think of a hot air balloon)

How do Volcanoes form?

The plates move over the stationary plume and lava rises to the surface

Is every volcano the same?

No, because the explosivity has a lot to do with the composition of the magma/lava

Why are Malfic volcanoes effusive?

Because their magma has low viscosity, it is runny

Why are felsic to intermediate volcanoes explosive?

Because of their high silica content and trapped gases, they are usually highly explosive; they contain more ash and rock fragments

What role does the viscosity of lava play?

It controls how easily gas can escape the lava when lava rises to the surface

What makes lava "sticky"?

The high Silicon content and temperature

What is Pāhoehoe lava?

Characterized by its "ropes," the runniest form of lava, very thin

What is A'a Lava?

Lava of thicker mass or slightly viscous basaltic lava

What are shield volanos?

Runny, low-viscosity lava can travel far from the central vent

What is a Lahar?

Mud flows or ash, water, and debris that are created by the heat of a volcano

What is a Lava Dome?

When lava is so sticky, it can't spread out very far, and it piles up

What are Stratovolcanoes?

steep-sided, conical volcano formed by felsic to intermediate lavas, covered in pyroclastic and Lahars

What is a pyroclastic flow?

a dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing downslope at great speed.

What are metamorphic rocks?

Formed by heat and pressure

What are three types of Metamorphism?

contact, regional, hydrothermal

What happens in low-grade metamorphism?

Low temp and pressure, Foliation

What is foliation?

When there is so much pressure, it can create elongated minerals perpendicular due to stress

What happens in low- to medium-grade metamorphism?

Crystals/clasts merge together due to the high pressure that generates heat

What happens to the clay minerals during metamorphism?

They become micas

What is solid-state diffusion?

movement of atoms through a solid to form a new mineral

What happens in high-grade metamorphism?

the rock is completely changed and there might be some banding

What are Earthquakes?

Occurs when there is a sudden movement along a fault due to stress buildup

How do Earthquakes work?

1. Stress builds up on a fault

2. Stress reaches a critical level

3. Stress is released as a quake

What is a fault?

A fracture in rocks along which there has been movement

What is the focus?

The point in the earth where the earthquake starts

What is the Epicenter?

the point on the surface directly above the focus

What is Displacement?

Movement along a fault

What is a fault scarp?

Surface evidence of the fault's motion

What makes a quake hazardous?

Magnitude, depth, distance, development, population density, rock type

What is liquefaction?

When a solid substance acts like a liquid due to high energy from the quakes

As magnitude increases,

energy increases

Based on your understanding of what controls the size, shape, and sorting of clasts, what type of sediment would you expect to find deposited on the beach?

Mostly coarse grained (sand), rounded and well sorted

Metamorphism associated with compressive plate tectonics is referred to as

Regional metamorphism

Metamorphism associated with compressive plate tectonics is referred to as

Regional metamorphism

Based on your understanding of what controls the size, shape, and sorting of clasts, What type of sediment would you expect to find deposited within a river

Sand to gravel and rounded clasts