ESC LAB Midterm
Dip
Angle of incline (0-90) degrees
More Physical Properties of Minerals
* Texture *magnetism *Specific Gravity *taste *Odor *effervesces With HCl
Physical Properties of minerals to describe them
* shape *luster *Color *Hardness *Streak *Cleavage
5 things that define a mineral
*Inorganic *naturally Occurring *Solid *Definite Crystalline Structure *Definite Chemical Composition
Hardness Scale
10. Diamond 9. Corundum 8. Topaz 7. Quartz 6. Orthoclase 5. Apatite 4. Fluorite 3. Calcite 2. Gypsum 1. Talc 6.5 is streak plate 2.5 is fingernail
Syncline
A fold with concave side upward Cross-section would show the youngest rocks in the middle
Anticline
A fold with convex size upward Cross-section would show the oldest rocks in the middle
Metamorphic grade
A measure of how much the rock was metamorphosed. Slate is produced through low grade metamorphism Gneiss is produced through high grade metamorphism Slate was metamorphosed at lower Temperatures (T) and Pressures (P), while Gneiss was metamorphosed at higher T & P
Luster
A reflective property of mineral surfaces
Metamorphic Rocks
A rock that has been altered in form due to heat, pressure , and or hydrothermally. has not been melted (is derived from protoliths)
Minerals
A solid inorganic substance of natural occurrence. Most mineral specimens are irregular grains, very few display their characteristic crystal habit.
Hotspots
An area of unusual volcanic activity Not associated with plate boundaries Plumes do not move
Hinge line
An imaginary line that all beds are "bent" around
Three types of deformation
Brittle *faults *joints Elastic Ductile *folds
Streak
Color of powdered mineral which is tested by rubbing the mineral across a porcelain streak plate
Rock cycle sediment
Compaction and cementation-> Sedimentary Rock
Strike
Compass direction (0-360)degrees
Mantle
Contains more than 82 percent of Earth's volume Physical properties vary with depth Behaves rigid in some areas and ductile in others
Parts of Lithosphere
Continental Crust Oceanic Crust Uppermost SOLID mantle
Intrusive igneous rock
Cool at depth. Means they cool at slower rates and therefore have larger crystals
Changes in metamorphic rocks form
Crystal Shape/size - this is called Recrystallization Rock/Mineral shape - high Temp allows rock to act ductile , allowing rock to be deformed by high Pressure Mineralogy - different minerals can form in the rock due to metamorphism.
Aphantic
Crystals are too small to see shows very fast cooling volcanic from lava
Fracture
Describes the inability of a mineral to break in a consistent way and therefore not along cleavage planes
Breakage
Determined by cleavage and breakage Cleavage: is the tendency of the mineral to break along flat planes of weaker bonding *Cleavage Planes 0+ Fracture: Cleavage is absent and mineral breaks irregularly
Convection cells
Drag and move the lithosphere plates
Crust
Earths relatively thin, rocky outer shell. Can be divided into continental crust and oceanic crust
Shape: Crystal Habit
Every mineral has a crystal form. The crystal form is the shape that a crystal will take if it grows unimpeded
Effervesces with HCl
Fizz or give off bubbles
Shield volcanoes
Formed by non-violent Basaltic lava flows Travel large distances before cooling Mainly under-water
Modern evidence of Plate Techtonics
GPS Earth's magnetic Field Paleomagnetism Distribution of earthquakes along plate margins Age dating sediments on either side of the ridge Thickness of sediments also increases away from ridge
Gneissic Banding
Gneissic Banding refers the alternating layers of light and dark minerals Mineral size is medium to coarse (visible to eye) Represents high grade metamorphism
Transport and Deposition
Grains are transported by wind or water, variable distances. Deposition occurs in various location and is directly related to the energy of the environment.
Earthquakes
Ground shaking caused by the sudden and rapid movement of one block of rock slipping past another along fractures in Earth's crust called faults he energy generated by an earthquake radiates outward in the form of seismic waves from the source of the quake, called the hypocenter, or focus.
Rock Cycle Sedimentary rock
Heat and pressure --> metamorphic Rock weathering and erosion-> sediment
Hot Spots
Injection of magma
Volcanic Hazards
Lava flows Lahars Pyroclastic flows Bombs Toxic gasses Acid rain
Divergent Plate boundary
MOR Sea Floor Spreading Upwelling of Molten Material Ocean-Ocean Continent-Continent
What are two types of sediment rocks
Made up of grains there are two types of sedimentary rocks : Chemical (biochemical) (formed through solution) Clastic (detrital) (or debris of any kind)
Core
Made up of iron-nickel alloy. Can be divided into liquid outer core and solid inner core
Where do different types of igneous rocks form
Mafic: oceanic crust is created at divergent boundaries. Hot Spots also tend to be mafic Felsic: A magma chamber that pushes itself through a continental plate tends to be felsic Intermediate: Volcanic Arcs
Rock cycle Metamorphic Rock
Melting---> Magma weathering and erosion-> sediments
Identifying Metamorphic Rocks
Metamorphic Names reflect chemistry and texture Two things to know to name rock: Texture type Mineral types present
How do rocks form
Molten Rock cools and igneous rocks are formed Metamorphic rocks are formed when pre-existing rocks are changed by temperature and pressure When loose grains/sediments undergo lithification, the result is sedimentary rock
Phyllite texture
No visible mica grains Glossy/bright sheen Wavy to wrinkled foliation of mica grains Weak slaty cleavage Represents low to medium grade metamorphism
regional metamorphism
Occurs over large areas due to tectonic processes Pressure involved is moderate to high Temperature involved is low to high Associated with batholiths (only because these are associated with regional tectonics), rock burial (subduction), folding, orogenesis, etc. caused by tectonics
Three types of seismic waves
P waves S waves Surface waves
Seven Major plates
Pacific Eurasian African Australian North American South American Antarctic
epicenter
Point on Earth's surface directly above an earthquake's focus
Rate formula
Rate = Distance/Time
Two types of Metamorphism
Regional Metamorphism Contact metamorphism
Dip- Slip Faults
Result of brittle deformation Dip-slip faults separate rocks into two "blocks" - Hanging wall - Footwall Normal Faults result in a lower hanging wall Reverse faults result in a lower footwal
Non foliated textures
Rocks that have no obvious layering main texture types:1 Crystalline (e.g. Marble) Microcrystalline (e.g. Hornfels Sandy (e.g. Quartzite) Glassy (e.g. Anthracite)
Magnetism
Some minerals are magnetic. This ranges from weakly to strongly magnetic
Taste
Some minerals exhibit a specific taste
convergent plate boundary
Subduction Zones Volcanic Arcs Island Arcs Ocean-Ocean Ocean-Continent Continent-Continent
Vesicular
Texture Contains vesicles (gas bubbles trapped in lava) Formed from depressurization of the magma. Often looks like a sponge
Glassy
Texture Looks like glass. Very rapidly cooling forms from volcanic glass no crystals present
Phanertic
Texture Visible crystals, shows slow cooling 1-10mm
Porphyritic
Texture two distinct crystal sizes Large ones and small ones Generally due to a change in the rate of cooling
Pegmatitic
Texture Very large crystals shows very slow cooling (plutonic)
Cleavage
The ability of a mineral to break or come apart in consistent way * breakage is along atomic planes *cleavage is consistent with crystal symmetry and may be one to multi-directional from one mineral to another
What do grains tell us about sedimentary rock
The grains of a sedimentary rock give us a story of origin of the grains and what type of environment the rock formed in
Lithification
The hardening of sediment through compaction and cementation This forms the rock
Geothermal gradient
The rate of temperature increase with depth within the Earth. Varies from place to place
Seismogram
The recordings made by seismographs. used to determine the time and location of earthquakes
Specific Gravity
The specific Gravity of a mineral is a comparison of its weight with the weight of equal volume of water. Specific gravity measures the density of a mineral
Luster: metallic
There are two types of metallic minerals: metallic and Sub-Metallic
Surface Waves
Transmitted along the surface
S waves
Travel through Earths interior Slower than p waves Only travel through solids
P waves
Travel through the earths interior have the greatest velocity travel through solids, liquids and gases
Strike Slip Faults
Two possible motions along a strike-slip fault - Left-Lateral (sinistral) -Right-Lateral (dextral) If you stood along the fault, the block that is coming towards you shows the motion of the fault
Composite Volcanoes
Usually Andesitic or Rhyolitic Steep slopes, and violent eruptions Sometimes called "Stratovolcanoes"
Cinder Cones
Usually basaltic with high gas content Gas escapes first, and launches pyroclastic material into the air Material accumulates to form the cone After gas escapes, basaltic lava flows are common
Luster: Metallic vs Non- Metallic
Usually, we begin by separating the metallic and Non-Metallic minerals. Minerals can be further divided into sub-categories based on luster. some minerals exhibit both metallic and non-metallic properties.
Evidence for direction and rate of plate motion
Volcanic islands created by hotspots allow us to track the rate and direction of plate movement. Youngest at the hotspot cool -> dense -> subside -> erosion -> Seamounts
Color
Wavelengths of visible light are absorbed or reflected by the mineral Some minerals change color or have various forms of different color Sometimes color is determined by trace elements You CANNOT rely on color when it comes to mineral identification
Conchoidal
a smooth, curved breakage in all directions
Luster: Non-Metallic
adamantine resinous glassy/vitreous pearly greasy/oily silky dull earthy
Three types of folds
anticlines synclines monoclines
Types of magma
basaltic (Mafic) -low viscosity andesitic (intermediate) -Moderate Viscosity rhyolitic (felsic) -high viscosity
extrusive igneous rock
cool at the surface they cool at faster rates and have smaller crystals
Rock cycle Magma
cooling--> Igneous Rock
3 main types of plate boundaries
divergent convergent transform
Sedimentary rock
formed from the accumulation and consolidation of sediment usually in layered deposits
Igneous Rock
formed through the cooling and solidification of magma or lava
5 types of properties looked for in grains of sedimentary rock
grain size Grain shape Sorting Fossils Chemical Properties
Seismographs
instruments that detect and record seismic waves
Weathering
is the process of breaking down rocks and minerals into smaller pieces by water, wind, and ice. This creates grains
Law of Orginal Horizontality
layers of sediment are originally deposited horizontally under the action of gravity. Metamorphic rocks typically keep the bedding orientation if they come from
Schistosity
minerals (e.g. mica) and/or linear alignment of prismatic minerals (e.g. tourmaline or hornblende) Minerals are visible Rock is covered in scaly/glittering layer of shiny minerals Can have wavy foliation Represents medium to high grade metamorphism
what is a rock
naturally occurring solid aggregate of one or more minerals or mineraloids
Protoliths
parent rocks Include: Igneous Sedimentary Metamorphic rock types
Foliation
refers to the layering and parallel alignment of mineral crystals. Foliation forms perpendicular to pressure
4 types of Foliation textures
slaty cleavage phyllite texture schistosity gneissic Banding
Sedimentary Structures
structures formed during or shortly after disposition some created by water others created by things such as footsteps
Grain sorting
tells us how far grain traveled and energy level of transportation Degree of uniformity of grain size: *well sorted: -grains are all the same size -low energy transportation -slow river -long travel time *poorly sorted: -Grains are different sizes - High energy transportation - I.e. debris slide, gravity flow -short travel time
Grain Shape
tells us how far the grain has traveled Rounded= more travel time Angular= less travel time
Grain size
tells us how far the grains traveled before deposition smaller the grain size, the further the grain has traveled Biggest to smallest: Gravel Sand Silt Clay
Pyroclastic
texture fragments of volcanic glass, ash, cinders, volcanic bombs
types of igneous rocks
ultramafic- rare, primitive, mantle derived mafic- Mg and/ or Fe rich, more dense, oceanic crust intermediate- mix of mafic and felsic felsic- Al and/or Si rich, less dense, continental crust
Rock Cycle Igneous Rock
weathering and erosion-> sediment Heat and pressure --> metamorphic Melting---> magma
How are sedimentary rocks formed
weathering- Transport and Deposition Lithification
Parts of Mantle
• Asthenosphere Upper mantle Lower mantle
Convergent deformation
• Folding and Faulting: Uplift Reverse Faults (Dip Slip) Thrust Faults (Dip Slip)
Parts of Core
• Inner Core Outer Core
Transform Plate boundaries
• Slide past one another Leaky transforms Transpression and Transtension (more in later classes)
transform Deformation
• Slide past one another Leaky transforms Transpression and Transtension (more in later classes) the formation of mini basins and ranges
Divergent Deformation
• Thinning of the crust• Subsidence Normal Faulting (Dip Slip) Spreading Upwelling of Molten Material Ocean-Ocean, Continent-Continent
Slaty Cleavage
•If it has slaty cleavage, it is Slate Slaty Cleavage refers to the way the rock breaks into tabular sheets, roughly oblique to perpendicular in respect to the foliated crystals (usually mica) No visible mica grains Slate usually does not have a sheen to it (though may have a dull sheen) - why would it have no to dull sheen? Represents low grade metamorphism
Layers of earth
•It was due to the variations in travel times of P and S waves that scientists were able to provide evidence for the division of Earth's interior into three compositionally distinct layers Crust Mantle Core
Contact Metamorphism
•Occurs locally, next to igneous intrusions, or from hydrothermal fluids from intrusions Pressure is low to moderate Temperature is moderate to high
Block Diagrams
● Representation of 3-D space in a 2-D image Used to show regional or local deformation Shows strike and dip symbols on the surface Axes of any folds Faults