Review Exam 3

The process of determining if one rock or geologic event is older or younger than another, without knowing their specific ages

Give rocks an actual date or date range in numbers of years

Assumes the same physical processes that are occurring
today have operated throughout geologic time

The law of superposition is one of the principles of geology scientists use to determine the relative ages of rock strata, or layers

Sedimentary (and some volcanic) rocks are created in
succession, with the oldest rocks at the bottom, and
progressively younger rocks above

Geologic features such as dikes and faults that cut across rock must
be younger than the rock they cut

Core
Inner – Solid iron
Outer – molten iron; magnetic field
generated
Mantle
Lower – rigid (solid); silicates rich in
iron and magnesium
Upper – more silicates
Upper Mantle
Rigid
Plastic (“mushy”)
Rigid
Mohorovicic (Moho)
Separates crust from upper mantle
Crust
Oceanic (more dense)
Continental (less dense)

Lithosphere
Rigid rock comprising the crust
(oceanic and continental) as well as
the underlying rock
Asthenosphere
Plastic or mushy upper part of the
mantle
Convective movements in this layer
drive movements of the crustal
plates

Rocks are made of minerals; a mineral is defined
Naturally occurring solid
Definable chemical composition
Possess a crystalline structure
‘typically’ inorganic

Silicates – silicon and oxygen
Oxides – oxygen and metallic elements
Sulfides & Sulfates – sulfur and metallic elements
Carbonates – carbon with oxygen and other elements

Silicates

Igneous rocks are formed from melted rock deep inside the Earth. Sedimentary rocks are formed from layers of sand, silt, dead plants, and animal skeletons. Metamorphic rocks formed from other rocks that are changed by heat and pressure underground.

Igneous rocks form from volcanoes diorite, gabbro

Metamorphics are deep within the Earth or where tectonic plates meet like where mountains meet diamonds, marble, quartz

often start as sediments carried in rivers and deposited in lakes and oceans. When buried, the sediments lose water and become cemented to form rock like sandstone or limestone

the gradual movement of the continents across the earth's surface through geological time.

A theory explaining the structure of the earth's crust and many associated phenomena as resulting from the interaction of rigid lithospheric plates which move slowly over the underlying mantle

Divergent boundaries -- where new crust is generated as the plates pull away from each other.
Convergent boundaries -- where crust is destroyed as one plate dives under another.
Transform boundaries -- where crust is neither produced nor destroyed as the plates slide horizontally past each other.

Tectonic activity
Driven by planet’s internal energy
Builds crust

Weathering and erosion
Powered by Sun through motion of air, water, and ice
Shapes crust

how rocks
respond to stress
Folding (bending)
Faulting (breaking)

force over a
given area
Tension (stretching)
Compression (shortening)
Shear (twisting and tearing)

3 types of faults
Normal
Thrust or Reverse
Strike-Slip (Left and Right Lateral)

Sudden movements along
plate boundaries, releasing
enormous amounts of energy
(magnitude)
Focus – spot along fault where
quake originates
Epicenter – point on surface
directly above the focus

- pours out a more liquid type of lava more
frequently (shield volcanoes and flood basalts)

has a more viscous type of lava that leads
fewer eruptions that are more violent
(composite/stratovolcanoes, lava domes and calderas)

Magmas that are more rhyolitic have a higher gas content. This gas content and relative viscosity leads to the more explosive and violent eruptions that occur at composite volcanoes

The main difference between the two is that a shield volcano is composed of basaltic lava while a composite volcano is composed of andesitic magma

Denudation is the name for the processes of erosion, leaching, stripping, and reducing the mainland due to removal of material from higher to lower areas like valleys, river valleys, lakes and seas with a permanent filling of low lands

Physical, or mechanical, weathering happens when rock is broken through the force of another substance on the rock such as ice, running water, wind, rapid heating/cooling, or plant growth

Chemical weathering occurs when reactions between rock and another substance dissolve the rock, causing parts of it to fall away

Physical weathring - fast moving water, Ice wedging, plant roots,

chemical - rust

A type of landscape where the dissolving of the bedrock has created sinkholes, sinking streams, caves, springs, and other characteristic features

When much of the water falling on the surface interacts with and enters the subsurface through cracks, fractures, and holes that have been dissolved into the bedrock

Any movement of a body of material under gravity
Requires a slope under influence of gravitational stress
Angle of repose – steepness angle that a pile of material
will form when it has stabilized
Categories include: fall, slide, flow, and creep
Human-induced mass movements is scarification

steepness angle that a pile of material
will form when it has stabilized

The fundamental transport processes to be able to describe the quantity and quality of water as it moves through the cycle

A drainage basin is a land area that drains its water into a waterway or waterways that result in common outlet

The boundary between drainage basins is a drainage divide

Inland basins that do not drain to an ocean

Drainage Density is the total length of all the streams and Rivers in a Drainage basin divided by the total area of the drainage basin.

The drainage pattern is the arrangement of channels in
an area, which is influenced by climatic and geologic
conditions
Dendritic drainage
Parallel drainage
Trellis drainage
Radial drainage
Rectangular drainage

Volume of flow over time (discharge)

The discharge of a river is just the volume of water passing a certain point every second, multiplying the cross sectional area of the river by its velocity.

A hydrograph is a graph of the flow in a stream over a period of time

A stream that derives much of its waters from a drainage system in another region

This material is then transported to new locations (fluvial transport)

Solution
Suspension
Saltation
Traction

However, many streams in steep mountain regions or in
bedrock-controlled channels have a relatively straight
channel pattern

In large river systems, an anabranching channel pattern
sometimes occurs, in which multiple large channels are
present across a vast floodplain

With excess sediment, stream
might become maze
of interconnected channels
forming a braided stream

A channel is a wide strait or waterway between two landmasses that lie close to each other

However, many streams in steep mountain regions or in
bedrock-controlled channels have a relatively *straight
channel* pattern

In large river systems, an *anabranching channel* pattern
sometimes occurs, in which multiple large channels are
present across a vast floodplain

With excess sediment, stream
might become maze
of interconnected channels
forming a *braided stream*

alluvial fans, terraces, deltas, and floodplains

Alluvial Stream Terraces
 Formed by phases of cyclic erosion
and deposition of alluvial sediments

River Deltas
 Mouth of a river →where river reaches base level
 River’s velocity decelerates as it enters standing body of water
 Reduced stream energy causes deposition of the sediment load
 Coarse sand deposits closest to river’s mouth
 Finer materials (silts & clays) are carried farther and form the
extreme end of the deposit
 The level or nearly level depositional plain that forms at the mouth
of a river is a delta

Floodplains
 Flat, low-lying area adjacent to a
channel and subjected to recurrent
flooding
 Area inundated when river overflows
its channel during times of high flow
 When water recedes, leaves behind
alluvial deposits masking underlying
rock with accumulating thickness
 The present river channel is
embedded in these alluvial deposits

The general term for the unconsolidated clay, silt, sand,
gravel, and mineral fragments deposited by running
water is alluvium
The processes of fluvial deposition occur when a stream
deposits alluvium, thereby creating depositional
landforms, such as bars, floodplains, and deltas

The Work of Wind
 Eolian means work of wind
 Eolian erosion is controlled by particle grain size
Intermediate – move easily by bouncing
Large – resist movement due to their weight
Small – resist movement due to their mutual cohesiveness
 Two principal types of wind erosion
Deflation – lifting and removal of individual loose particles
Abrasion – grinding of rock surfaces via “sandblasting”
 Produce a variety of distinctive landforms

Erosional landforms: Caves, arches, stacks and stumps

Depositional landforms: beaches, spits and bars

Three climate controls of deserts
 Subtropical highs (25-35ºN&S)
 Rain shadows of mountains
 Continentality

 Common characteristics of deserts
 High sensible heat
 High ground heating
 Low PRECIP, high POTET, leading to large DEFIC
 Intermittent streams

Desert Fluvial Processes and Landforms
 Wash (arroyo) – a dry stream bed
 Flash flood – sudden torrent of water that fills a channel
 Slot canyon – long, narrow channel with sheer rock walls
 Playa – a dry lake bed
 Alluvial fan – fan-like deposit of sediments at the mouth of a canyon
stream
 Bajada – broad slope composed of several alluvial fans

The process of land degradation in arid, semi-arid and dry sub-humid areas as a result of various climatic and human factors.

Extended droughts and deforesting/ vegetation removal

Loss of biodiversity by worsening the living conditions of many species

A rain shadow is a patch of land that has become a desert because mountain ranges block much of the rainfall necessary for plant growth