universe & the earth pt. 2 (mod #2)

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1. body waves

2. surface waves

2 TYPES OF SEISMIC WAVES:

1. these travel through the interior of the earth

2. move only along earth’s crust

p-waves / primary / pressure waves;

2 TYPES OF BODY WAVES:

Formed from alternating compressions and rarefaction;

Arrives first;

Travels through gases, liquids and solids

s-waves / secondary/ shear waves

2 TYPES OF BODY WAVES:

Formed from oscillation perpendicular to wave direction;

Dependent on shear stress;

Arrives second

1. Love waves

2. Rayleigh waves

2 TYPES OF SURFACE WAVES:

1. fastest surface wave, side to side

2. rolling, up-down, most shaking

xenoliths

EARTH’S LAYER (EVIDENCE):
Inclusions in igneous rocks during emplacement and eruption that typically originate from the upper mantle;

provides information about the composition of the mantle

xenocryst

EARTH’S LAYER (EVIDENCE):

Individual foreign crystal included within an igneous rock

meteorites

EARTH’S LAYER (EVIDENCE):

Debris or material on a surface of a planet (Earth) that originated from outer space;

May come from meteoroids, asteroids, comets, moons or planets;

Chondrite

TYPES OF METEORITES:

undifferentiated (contains chondrules)

Chondrules

TYPES OF METEORITES:

round grains that formed from molten (/partially) droplets

Achondrite

TYPES OF METEORITES:

differentiated (depleted in meteoric iron mafic/ultramafic)

Stony iron meteorites

TYPES OF METEORITES:

differentiated (equal meteoric iron and silicates)

Iron meteorites

TYPES OF METEORITES:

differentiated (planetesimal cores)

stony meteorites

TYPES OF METEORITES:

consists largely of silicates

continents

EARTH’S LARGE SCALE FEATURES:
very large landmasses, exposed above sea level;

includes mountain belts and plains up to the continental shelves

associated with continental crust & lithosphere

continents, 29.1%, Mt. Everest

EARTH’S LARGE SCALE FEATURES:

Area: 148,647,000 km²

this accounts for ____% of Earth’s surface area

• Highest Point: 8,848 m (_____ – Nepal)

mountain belts

EARTH’S LARGE SCALE FEATURES:

Chain of mountains that were formed from the same event (orogeny)

orogeny, orogenesis

EARTH’S LARGE SCALE FEATURES:

mountain-building event;

deformation of the lithosphere along convergent margin;

thickening, crumpling associated with volcanism

process: ______

ocean basins, 70.8%

EARTH’S LARGE SCALE FEATURES:

areas below sea level;

Area: 361,132,000 km2

Accounts for ____% of Earth’s surface area

ocean basins, Challenger’s Deep - Mariana Trench

EARTH’S LARGE SCALE FEATURES:

Includes abyssal plains, seamounts, trenches and mid-ocean ridges;

associated with Oceanic crust and lithosphere

deepest Point: 10,929 m (_____ ____ - _____ ______)

mid-oceanic ridges; divergent

Submarine mountain chain;

________ Plate Boundaries (Oceanic) – seafloor spreading

• Length: 65,000 km

• Global (interconnected)

oceanic trench

Elongate submarine depressions and deepest parts of the oceans;

convergent plate boundaries (Subduction Zones);

located parallel to volcanic and island arcs

seamounts

Elevated submarine structure;

Form from extinct volcanoes;

Typically conical

• ex. Bear ____ (Guyot)

guyot

flat-topped seamount

abyssal plains

EARTH’S LARGE-SCALE FEATURES:

submarine plain between the continental rise & mid-ocean ridges;

depth: 3000-6000m

principle of isostasy

Isostatic Equilibrium;

low-density crust “floats” above the high-density mantle rocks;

Continental mountain belts have roots that are mostly “submerged”

isostatic adjustment

process of establishing a new gravitational balance in response to loading or unloading

Airy-Heiskanen model

Crust with constant density;

Topographic heights accommodated by changes in crustal thickness;

iceberg analogy

• root & antiroot

1. root

2. anti-root

TYPES OF ROOTS:

1. under mountains (deep)

2. under oceans (shallow)

Pratt-Hayford Model

Lithosphere with equal depth;

Crust with varying density;

topographic heights accommodated by lateral changes in density;

Isostatic Compensation

Vening Meinesz Model

Flexural Isostasy Model;

Regional Isostasy;

elastic lithosphere

• downwarp & rebound

1. downwarp

2. rebound

2 OF EARTH’S VERTICAL MOVEMENT:

1. addition of load (ice sheet, orogen)

2. removal of load (deglaciation, erosion)

no isostasy

KINDS OF ISOSTASY:

T_e > λ

• elastic thickness T_e of the lithosphere is greater than the wavelength (λ) of an applied surface load, meaning the tectonic plate is rigid enough to support the load without flexing significantly

regional/flexural isostasy

KINDS OF ISOSTASY:

T_e ≈ λ

• how the Earth’s outer rigid shell—the lithosphere—bends like an elastic plate under massive surface

• this strength allows the plate to distribute weight across a broader area, supporting loads through a combination of buoyancy and elastic forces

low flexural rigidity (otw to local isostasy)

KINDS OF ISOSTASY:

T_e « λ

• means that the lithosphere behaves as if it has virtually no mechanical strength

• lithosphere cannot support the load elastically.

• weight is compensated purely locally directly beneath the load.

  • Large scale continents or wide plateaus.

local isostasy

KINDS OF ISOSTASY:

T_e ≈ 0

• the lithosphere behaves like a completely broken, segmented, or infinitely flexible sheet.

• Any geological load placed on the surface is compensated entirely locally by pure hydrostatic equilibrium (buoyancy) alone