GEOG101 Part #4: Units 27 - 34

Elements

Exist independently or in combination of other elements. Consists of three parts: protons, neutrons, and electrons. 

Protons

Subatomic particle with a positive charge

• no. of protons = the atomic number

Neutrons

Subatomic particle with NO CHARGE

Electrons

Subatomic particle with a negative charge 

5 Identifications of Minerals

Naturally occurring, inorganic, solid compounds with a definite chemical composition and a crystalline structure/specific atomic arrangment.

Minerals are formed in…

plate tectonics, magma chambers, chemical reactions, & Bowen’s reaction series

The 6 physical properties of minerals are… 

Hardness, chemical composition, cleavage, luster, color, and streak 

Hardness 

Moh’s hardness scale of 1-10 

Chemical Composition

The chemical elements contained in a mineral

Cleavage 

Mineral’s tendency to break in certain directions to form bright plane surfaces/the structure’s zone of weakness 

• can have more than 1 direction 

Luster

A mineral’s surface sheen; does the mineral reflect light, Vitreous (glassy), opaque, or dull

• metallic or nonmetallic

Streak

The color displayed by the finely powdered remains of the mineral

What are the two types of minerals?

Silicate Minerals and Nonsilicate Minerals

Silicate Minerals

Made up of silicon and oxygen.

• crystalline structure consists of one silicon atom bonded to four oxygen atoms, forming a tetrahedron

What are six Nonsilicate Minerals?

Include carbonates, sulfates, sulfides, halides, oxides, & natural elements

What are the three rock types?

Igneous, Sedimentary, and Metamorphic

Igneous Rock

Formed as a result of cooling magma/lava until solidified (rock solidified from a silicate liquid)

• if made from magma —> intrusive —> plutonic

• if made from lava —> extrusive —> volcanic

Intrusive Igneous Rock

Formed through the solidification of magma, cooling slowly and allowing for large crystal formation

What are the five different TYPES of Intrusive Igenous Rock?

Batholith, stock, sill, dike, and laccolith

Batholith 

Massive body of intrusive rock that melted & assimilated many of the existing rock structures that it invaded 

Stock

Similar to a batholith, but smaller

Sill

When magma inserts itself as a thin layer between strata of existing rocks without disturbing older layers to any great extent (horizontal)

Dike 

When magma cuts vertically across existing layers and forms a barrier wall 

Laccolith

When a magma pipe leads to a growing, dome-like chamber that pushes the overlying strata into a gentle bulge without destruction

• high viscosity —> magma stays compact

Viscosity

A fluid’s resistance to flowing

Extrusive Igneous Rock

Formed through the solidification of lava, cooling very quickly and not allowing for mineral growth (crstyals are not visible) 

• fine grain, glassy texture

How are felsic and mafic rock formed? 

Formed from cooled magma 

Felsic Rock

Magma rich in silica, light colored, rich in silicon

Mafic Rock

Magma poor in silica, dark colored, rich in iron/magnesium

Silica

A hard, unreactive, colorless compound which occurs as the mineral quartz and as a principal constituent of sandstone and other rocks.

Examples of Felsic Rock 

Granite & Rhyolite 

Examples of Mafic Rock

Gabbro & Basalt

Jointing

Develop parallel sets of fractures without obvious movement along the plane of separation

• due to rapid cooling

• contracting rocks create planes of weakness

Exfoliation 

Forms shell-like patterns, caused by release of compression/confining pressure 

Sedimentary Rock

Rocks resulting from the compaction and cementation of sediments

• weathering & erosion 

Processes of sedimentary rock formation:

Lithification, compaction, and cementation

Lithification

Loose rock sediment transformed into rock through compaction and cementation

Compaction

Packing of sediments into smaller volume

Cementation

Gluing of sediments

What are the different TYPES of Sedimentary Rock? 

Clastic and Nonclastic 

Clastic Rock

Made from the particles of other rocks (sandstone, shale, conglomerate)

Nonclastic Rock

Formed from chemical solutions/organic deposition

Stratification

Natural layering of rocks where each layer/stratum represents sediment deposited during a certain period.

Unconformity

Contact between eroded strata and the strata of resumed deposition

Metamorphic Rock

Rocks underground that are changed as a result of exposure to intense heat and/or pressure

Contact Metamorphism 

Whenever an existing rock comes into contact with magma or lava, it is burned/changed from that heat. Nearby batholiths or dikes are affected. 

Earthquakes

Generate pulses of energy known as seismic waves that can spread out from their source through the entire Earth

• seismic waves take time to travel through the planet

Seismic Reflection

When seismic waves reach an abrupt change in density and rigidity, they are bounced back

P Waves

Primary waves; congressional & fastest. Moves through solids, liquids, and gases.

S Waves 

Secondary waves; shear and slower than P waves. Only moves through solids 

Continental Crust

Made up of low-density, felsic (more silica content) rock

What is the most common felsic igneous rock?

Granite

Oceanic Crust

Made up of high-density, mafic (low silica content) rock

What is the most common mafic rock in oceanic crust? 

Basalt 

Lower Mantle

Lies above the outer core. Made up of iron, magnesium, and silicon compounds.

Upper Mantle

Less dense, consists of two layers

First layer of the Upper Mantle

Mostly solid, quite plastic, and contains small percentage of molten rock (reducing velocity of P & S waves)

Second layer of the Mantle 

The uppermost part of the mantle, located beneath the crust and strong enough to remain rigid under stress 

• the Lithosphere is near this layer of the mantle

Lithosphere

Rigid, solid outer layer of Earth, made up of the crust and the uppermost part (second layer) of the mantle)

Asthenosphere

Part of the upper mantle below the lithosphere where hot rock is plastic and flows readily under stress

Inner Core 

Solid and composed of iron and nickel (750 mi thick)

What are the three main components that make up Earth’s internal structure?

Crust, Mantle, and Core

Outer Core

Liquid, molten state and composed of iron and nickel (1400 mi thick)

Topographic Relief

The vertical difference between the highest and lowest elevations in a given area

Mantle Diagram

Subduction (Process)

When a piece of oceanic crust collides with the continental crust, sliding beneath the continental crust.

• subducted oceanic crust sinks deeper and deeper into the mantle until it reaches the bottom

Where are subduction zones formed?

Beneath areas of cold, sinking mantle

How are mid-ocean ridges and rift zones formed?

Formed from a hot, upwelling mantle.

Slab-Pull Force 

When subducting oceanic crust sinks in to the mantle, creating a suction-like force which PULLS the subducting slab further into the mantle 

What is the main force that causes plate tectonics?

Slab Pull

Mantle Plumes

Cylindrical areas of hot, rising mantle

Hotspots 

Region of Earth’s mantle that is extremely hot, activating mantle plumes that break through the crust to form volcanoes 

The Outer Core exhibits… 

Convection, which carries heat into the mantle 

Are ranges of tall mountains/deep valleys associated with high or low topographic relief?

High Relief

Are flat plains associated with high or low topographic relief? 

Low Relief 

Continental Shields

Large, stable, relatively flat (low relief) expanses of extremely old metamorphic and igneous rock.

Wegener’s Hypothesis

Alfred Wegener proposed that Earth’s landmasses were once united in a giant supercontinent (Pangaea), which eventually broke apart (creating continents and oceans)

Evidence of Wegener’s Hypothesis/Pangaea

Fossils, Rock, and Glacial Deposits

Seafloor Spreading 

Magma rises from the Earth’s mantle, cools, then solidifies into igneous rock at divergent plate boundaries, creating a NEW ocean floor. 

Divergent Boundary

Plates that move apart

Convergent Boundary

Plates coming together

What are the different convergent boundaries?

• oceanic to oceanic

• oceanic to continental

• continental to continental (no subduction zone)

Transform Boundary

Slides past one another

Convection Cells

Act as a slow, powerful conveyor belt pushing and pulling Earth’s plates, causing them to diverge, converge, or slide past one another

Isostasy

Equilibrium between floating landmasses and the dense rock between them

What are the different types of volcanoes?

Composite, Shield, and Cinder Cones

Composite Volcanoes 

Steep-sided, conical volcanoes built from alternating layers of lava, ash, and pyroclastic material. Consists of immediate to felsic magma/lava content 

What are the two types of composite volcano flows?

Lahar Flows and Pyroclastic Flows

Lahar Flows

Major eruption with hot ash melting the snow and ice, forming a flood of ash, mud, and water rushing downslope.

Pyroclastic Flows

Outburst of hot gas and glowing volcanic ash particles (accompanying explosive eruptions of composite volcanoes).

Shield Volcanoes 

Mainly built up by lava flows produced by fluid basaltic, low-silica magmas. 

Cinder Cones

Produced by magma with intermediate to low silica content. This creates pyroclasts and lava flows.

Pyroclast

Fragments of volcanic material ejected in the air during an eruption.

Volcanic Calderas 

Basin created by rapid emptying of a magma reservoir, ceasing to support the volcano and allowing the ground surface to collapse over a large area. 

Focus

Where inside the Earth the rupture occurs

Epicenter

Where ON Earth’s surface the earthquake occurs (directly above the focus)

How are earthquakes measured?

Earthquakes are measured in magnitude (energy released) and intensity (severity of shaking)

What are the two types of magnitude scales?

Richter scale and the moment magnitude scale

Richter Scale

Assigns a number to an earthquake based on the measurement of the physical force of the ground motion.

Moment Magnitude Scale

Similar to the Richter and new scale, but calculated by the U.S. Geological Survey.