EarthSc 1121H Midterm 1

Quantity of Galaxies and Stars

# Galaxies = 2 x 10^11 to 2 x !0^12 # Stars per Galaxy = 10^11 # Total Starts = 2 x 10^22 to 2 x 10^23

Asteroid belt with relation to Jupiter

- Asteroids vary in size from small grans to object more than 1,000 km across - It is thought the immense pull of Jupiter's gravity prevented this material from aggregation to form a planet

KT Extinction evidence

- Based on presence of layer of clay rich in Iridium at K-T Boundry at Gubbio, result of collision, Ir rare in terrestrial rocks, common in some meteorites - Iridium rich later now found globally at K-T boundary - Glass spherules, glassy fragments, shocked (strained) quartz

Saturn

- Best known for it's systems rings made up of particles of rock and ice - Jupiter, Uranus and Neptune also have ring systems - At least 62 moons orbit Saturn

Problems with KT Extinction

- Crater located on Yucatan Peninsula - Crater possibly too old - Other extinctions have no evidence for impacts - Recent work seems to favor hypothesis that massive volcanic eruptions in India cause, or at least played a role in the extinction event

Examples of Natural Hazards

- Earthquakes - Tsunamis - Vulcanic Eruptions

View of the earth

- First seen in the Lunar missions - The presence of a thick atmosphere and hydrosphere are unique - Earth is the only known planet with abundant life - The view of the earth rising over the horizon of the moon, first seen in the Lunar missions in 1968. Note the the lack of thick atmosphere and hydrosphere and the barren surfaces on the moon

Jupiter's moons

- Io is Volcanically active - Europa is ice covered - Ganymede has a diameter of 5,268 km, is larger than Mercury, and is the ninth largest object in the solar system

Asteroids/Meteorites

- Largest asteroids show evidence of collisions or impacts (formation of craters) - Ida (56 km long) has a near spherical moon (Dactyl) - Asteroids nudged out of orbit by collisions. May also be fragmented by collisions - May travel on average at 90,00 km/hr (note E - 1/2mv^2, energy release on impact [average impact velocity - 65,000 km/hr for asteroids, 108,000 km/hr for comets] is enormous!)

Impact Crater Examples

- Meteor (Barringer Canyon Diablo) Crater [50 meters diameter, Arizona is 1200 meters in diameter] - Reis in Bavaria, Southern Germany [25 km diameter'], medieval wall town Nordlingen built in crater, Shoemaker discovered from church walls (diamonds)

Examples of Earth's Resources

- Oil drilling rig - Oil pipelines - Natural gas drilling rig - Shale formations - Copper mines - Limestone quarries

Importance of Knowledge of Earth Sciences

- Provides an understanding of the planet (its origin, evolution and of the processes that operate within it) - Provides awareness of natural phenomena and their effects - Allows informed appraisal of natural resources (e.g. coal, oil, water, minerals, metals) - Essential for discovery and exploitation of new sources of raw materials - Gives a better, more realistic understanding of the environments - Allows realistic evaluation of natural and man-made hazards, essential for accurately assessing and predicting hazard, and for alerting local, state, and federal authorities to the potential impact of hazards, allows "scaremongering" to be avoided

Man-made Hazards

- Radioactive-waste (high-level) from nuclear reactors - Household waste: Landfills can contaminate water supplies - Human and animal waste: Sewage can pollute water supplies - Industrial waste: Chemicals and acids can kill vegetation. animals and humans, atmospheric pollutions with CO2 and SO2 produces acid rain, ozone depletion, and global warming

Mars

- Smaller than earth. From a distance looks like a barren, dry, lifeless planet. - Canyons on the Martian surface that are similar to drainage patterns on earth - Water or ice formed these features. - Volcanoes also occur -Mons olympus is the size of Ohio and is 23 km (75,000 ft) high - Mars has two moons (Phobos and Deimos)

Jupiter

- The largest of the outer planets - Consists mostly of hydrogen and helium - May have rocky and metallic material in the core - At least 63 moons

Life on Mars

- The possible presence of water on Mars leads to speculation that life may have existed on this planet - Reports of the discovery of "fossils" in the 1990's fueled such speculation, but the evidence has been refuted (similar structures are produced by inorganic processes)

Density of core

11,000-13,000 kg m^-3

Density of crust

2,700-3000 kg m^-3

Density of mantle top

3,300 kg m^-3

Formation of the solar system complete about...

4.6 billion years ago

Density of mantle base

5,500 kg m^-3

Earths radius

6370 km

KT extinction

65 million years ago; dinosaurs and other animals of the time went extinct, discovered by Alvarex

Syrene is about ___ km south of Alexandria

800

Theory

A generalization about natural phenomena

Protoplanetary disk

A large disk-shaped cloud of dust and gas formed as the solar nebula rotated faster and flattened out. Dust and gas swirl around it, gradually forming into planets and asteroids. A few billion years ago, this is what our Solar System probably looked like.

Hypothesis

A plausible, but unproved , explanation for the way something happens, testable

The Scientific Method

A step by step process scientist use as a research strategy

Earth's Characteristics

A unique, dynamic planet. Earth is constantly changing. No other planet in the solar system currently has the right chemical and physical mix needed to support life. No conclusive evidence of life existing elsewhere in the universe has yet been discovered as far as we know.

The Solar System and Asteriods

Asteroids occasionally collide and are knocked out of orbit. They can then collide with other object (e.g. planets) in the solar system.

Interactions

Atmosphere -> Biosphere -> Lithosphere -> Hydrosphere The eruptions from Tambora (1815) and Laki (1783) demonstrate interactions between various components of the earth system

Science

Attempt to understand nature, the natural world, and natural phenomena; Simply - the expression of human curiosity

Physical Geology

Concerned with earth materials: changes within and at the surface of the earth; processes operating within and at the surface of earth

Earths shells

Core, Mantle, Crust, Hydrosphere, Atmosphere Largely solid, composed of rock

Impact Craters Hazards

Impacts are very common. Large impacts may disturb the environment sufficiently to affect life of earth. It is hypothesized that an impact 65 million years ago led to extinction of the dinosaurs and other organisms.

Nebular hypothesis

Matter formed in an earlier supernovae (or supernovae) forms a denser mass due to shocks from nearby exploding stars and gravitation attraction. As the cloud rotates, most matter collects at the center. Collisions of particles produces a hot proto-sun (proto-star) at the center. Continued rise in temperature to 10,000,000 degrees celsius and rise in pressure allow onset of hydrogen fusion to form sun (star). Collisions generate heat. The outer part of the gas cloud in protoplanetary disk cools allowing condensation of material to form dust particles. These accrete by collision into clumps, larger planetesimals that grow into protoplanets and, eventually, planets at fixed distances from the sun.

Asteroids, meteorites and impacts

Meteorites frequently collide with earth. The largest impacts leave large impact craters. Meteorites provide information about the origin of the solar system, - Energy release is enormous [given by equation for kinetic energy)

Earth's interior was studied by...

Mohorovicic 1909 - crust-mantle boundary (Moho) Gutenberg 1913 - core-mantle boundary Lehmann 1936 - inner-outer core boundary

Origin of the Moon

Moon forms as the result of collisions between Earth and Mars-sized impactor (Theia) within 50 my of formation in solar nebula

Earth-Moon Systems

Moon forms through collisions of earth and large (mars-sized) impact [latest/accepted hypothesis]

The Sun

More than 99% of all matter in the solar system is contained in the sun. Radiation from the sun heats the surface of earth and this heat drives processes at the surface.

Saturn's moons

TItan is the second largest moon in the solar system (after Ganymede) with a diameter of 5,149 km, and is larger than Mercury

Aggregation and temperature

Temperature varies across nebula. Heavy (high Z) elements concentrate in inner nebula, light (volatile) elements concentrate in cooler, outer nebula (differentiation).

Origin of the earth

The Nebular hypothesis was developed by Emanuel Swedenborg (1730's), Immanuel Kant (1755), and Pierre Laplace (1796). Generally accepted today.

The Solar System

The central sun and orbing planets. Inner "rocky" or "earth-like" planets and outer "gas-giant" or "Jovian" planets.

Moon

The moon (and Mars) is intensely cratered. The craters reflect impacts with objects similar to asteroids. Most of these impacts are thought to have occurred early in the history of the solar system (although the dates of many craters are unknown)

Stars compared to Sand

The number of stars in each galaxy and the number of stars in the universe is staggering. The number of stars in the universe is greater than the total number of grains of sand on all the beaches on earth.

Sun/Earth in Perspective

The sun is a relatively small star in the milky way galaxy and the earth is a medium-sized planet orbiting the sun

Ice on Mars

There are "ice caps" in the polar regions of Mars - although these consist of water-ice and solid carbon dioxide. Recent evidence (Mars rovers, satellite data) indicate water on mars in the polar ice caps and as sub-surface ice.

Earth spins rapidly on an...

axis of rotation

Increased pressure and constant mass...

density increases

Meteorites have...

different types, important types were iron and stones Iron-nickel meteorite (similar composition to core) Cl Chondrite (similar composition to sun = solar system)

Core is made of...

iron (Fe) with some nickel (Ni)

This led to the hypothesis that there was...

iron in the interior of earth (10th most abundant element, some meteorites consist of it)

The Presence of iron at depth leads to possibility that interior is...

is layered, has structors

Earth has a...

layered structure, boundaries between different material/material with different physical properties

S waves cannot travel through...

liquid or air (fluids)

Mantle is made of...

mostly oxygen (O), magnesium (mg) , silicon (Si), iron (FE)

The Structure of the earth's interiors is determined from...

seismic waves

Seismic discontinuities

sharp changes in wave velocities over small depth intervals, mark boundaries between different layers or shells of the earth

Seismic wave velocities increase with...

strength (rigidity) and density of the medium through which they travel

As the depth of earth increases...

velocity increases (reflects increasing strength [rigidity] and density of rocks with depth)

Increased pressure...

volume decreases (also true for solids)

Evidence of that earth's core consists of an outer and inner core

Refracted P waves arriving at stations at angels greater that 142 degrees from the source indicates refractions at a boundary within the core

Key Aspects of the Scientific Method

1. Seek explanation of phenomena through objective analysis of observation or of measurements. May be difficult, but aided by the feedback from others (e.g. at conferences). 2. Must be flexible - willing to abandon cherished ideas in light of data/observations. 3. Must resist temptation to ignore or falsify evidence (data/observations) that are not consistent with hypothesis. 4. Ultimate test - peer review system prior to publication. even this is not infallible, but errors eventually detected by other scientists. Science is self-policing.

Scientific Method Steps

1. Select problem/phenomenon of interest. 2. Collect data. 3. Purpose hypothesis (allow predictions, testable). 4. Test hypothesis/test predictions (by comparing the predictions against new observations of data). 5. Reject hypothesis or formulate a theory. 6. Test theory. Make and test predictions. If theory fails test, propose new hypothesis. 7. If tests successful, EVENTUALLY formulate a law or principle. 8. Continually reexamine the law or principle in the light of new evidence.

Composition of the earth is inferred from

1. Composition of the sun (constitutes 99 % of the material in the solar system) 2. From meteorites (material that did not aggregate to form a large planet) 3. From sample of mantle brought to surface in volcanic eruptions

Characteristics of Science

Based on facts or observations about nature, not beliefs. Predictive, falsifiable (testable). Involves observing measuring, thinking, and testing, not believing.

What tells us there must be very dense material in the interior of the earth?

Earth density = 5509 kg m^-3, Densities of rocks in curst much lower than this (1600-3000 kg m^-3)

Kinetic Energy

Energy possessed by a body by virtue of being in motion

Environmental impact

Environmental effects of large impact (dust causing cooling etc) likely to be enourmous

Formation of planets

Formation of nebula observed in other constellations such as Orion. Stars with planetary systems form from these nebula by condensation of gaseous matter and aggregation of solid matter to form rotating cloud. Condensation and aggregation may be triggered by shock waves from nearby stellar explosions.

Rotation of Earth was proven by...

Foucaults's pendulum in 1851, pendulum swings back and forth in the same plane, Earth's rotation moves the ground beneath the pendulum

How was the Mass of Earth determined?

From Newton's Law of Gravitation Attraction. First determine mass of earth (Mass = Volume x Density) and volume is related to radius of a sphere by V = 4/2 pi R^3.

Jupiter Moons Proportions

Ganymede is 8% larger than mercury, .8 times the size of Mars and .4 times the size of Earth

Seismic Waves

Generated by earthquakes, body waves travel though the earth, they are reflected and refracted at boundaries between layers in the earth

Inner Planets

Inner "rocky", "earth-like" or terrestrial planets closer to sun - high T in nebula, form from materials with high T melting points (iron, nickel, silicates) (heavier elements, quite rare, forming only about .6% of mass of nebula)

Who created a View of Delft?

Johannes Vermeer

Jupiter vs Earth

Jupiter is about 1/1000 times the mass of the sun and just over 11 times the diameter is the earth

Mass pressure density equation

Mass = Density X Volume

S-wave shadow zone

No S waves (not even refracted waves) are received at station at angles > 103 degrees (indicates that part of the core is liquid because liquids cannot transmit through S waves)

P-wave shadow zone

No direct P-waves are received at seismic stations between 103-142 degrees from the source > 142 degrees (provides evidence that earth has a core)

Data

Observations, measurements

For a fixed mass of perfect gas at constant temperature...

PV = RT or PV = constant

Spiral galaxy

Part of the Milky Way can be seen at night, and is a spiral galaxy. The solar system is located in one the spiral arms.

Asteroid belt

Planetesimals and debris that did not aggregate because of Jupiter's gravity

Meteorites

Provide information about chemical composition of the solar system

Who determined Earth's Size and how?

Originally determined by Erasthenes in 250 BC form angle of incidence of suns rays at zenith at Alexandria and Syrene. Angle between suns rays at zenith and vertical at Alexandria is 7.2 degrees where the angle is 0 degrees at Syrene at the same time.

Outer planets

Outer "Jovian" planets (gas giants) further from sun, lower temperature, formed from solid , volatile icy compounds (ice, solid methane). Large size - capture hydrogen and helium. Gas giants account for approximately 99% of all the mass orbiting the sun.

Two types of seismic body waves generated by earthquakes

P (primary waves) and S (Secondary) waves

Which seismic waves travel faster?

P waves

A time-lapsed photo of ___ shows this rotation. One spin ___ km per day or ___ kph (___ mph). Rotation centered on _____.

Stars 40,000 1,700 1,040 Polaris, the North Star

Birth of stars and galaxies

Stars and galaxies form from cloud of gas and dust, which are presumably produced by supernovae.

Law/Principle

Statements that some natural phenomenon is invariable observed to happen in the same way, and no deviations have ever been observed

Geology

Study of earth. From Gaea (Greek Goddess of the earth) and logia Latin for discourse. Involves Earth interior, surface, history, origin/history of life, natural resources, hazards. Overlaps with and draws from Physics, Chemistry, Astronomy, Biological Sciences.

Underlying Philosophy of Science

Universe is orderly, ever effect has a cause. Seek explanation of phenomena through objective analysis of observations or of measurements

The Universe

Vast regions of "empty" space. Matter occurs in clusters (nebula, galaxies etc.)

Apophis

Will pass extremely close to the earth on April 13th 2029 and 2036, relatively small, chances of impact are small although the asteroid will pass between earth surface and orbit geosynchronous communications satellites, visible from part of earth surface

Crater located on __ with diameter of ___ was though to cause extinction of dinosaurs

Yucatan Peninsula, ~180 km

Density increases...

with depth in the earth