Open Earth Systems: An Earth Science Course For Maryland Teacher Professional Development EARTH HISTORY AND THE FOSSIL RECORD DAY 1 - Weds. July 9 AM Instruction:

Open Earth Systems: An Earth Science Course For Maryland Teacher

Professional Development

EARTH HISTORY AND THE FOSSIL RECORD

DAY 1 - Weds. July 9AM Instruction: Solar System Origin, Early Earth & HabitabilityAM Activity: Dating the Earth – Simulating Radioactive DecayPM Instruction: Major Events in Earth HistoryPM Activity: Exploring Geologic Time with TS-CreatorDAY 2 - Thurs. July 10AM Instruction: Climates of the PastAM Activity: Weathering, Erosion and SoilsPM Instruction: The Fossil Record of LifePM Activity: Fossil Identification

LINDA HINNOV, Instructor

OUTLINE

• Origin of Solar System

• The Planets

• Meteorites

• Early Earth

• Habitability

Our Solar System formed about 5 billion years ago, from an enormous cloud of dust and gas, a nebula. The Sun, like other stars, was formed in a nebula, an interstellar cloud of dust and gas (mostly hydrogen). These stellar nurseries are abundant in the arms of spiral galaxies (like our galaxy, the Milky Way). Dense parts of clouds in these nurseries undergo gravitational collapse and compress to form a rotating gas globule.

Origin of Solar System

According to a new model outlined in a study in the July 1, 2010 issue of Astrophysical Journal Letters, a shock wave from an exploding massive star (supernova) several light-years away probably triggered the collapse of the molecular cloud that would become our sun and planets.

The globule is cooled by emitting radio waves and infrared radiation. It is compressed by gravitational forces and shock waves of pressure from supernovae or hot gas released from nearby bright stars. These forces cause the roughly spherical globule to collapse and rotate. The process of collapse takes from between 10,000 to 1,000,000 years.


Central core and protoplanetary disk: As the collapse proceeds, the temperature and pressure within the globule increases, as the atoms are in closer proximity. The globule rotates faster and faster. This spinning action causes an increase in centrifugal forces (a radial force on spinning objects) that causes the globule to have a central core and a surrounding flattened disk of dust (called a protoplanetary disk or accretion disk). The central core becomes the star; the protoplanetary disk may eventually coalesce into orbiting planets, asteroids, etc.


Protostar: The contracting cloud heats up due to friction and forms a glowing protostar; this stage lasts for roughly 50 million years. If there is enough material in the protostar, the gravitational collapse and the heating continue.

A Newborn Star and a Solar System: When a temperature of about 27,000,000°F is reached, nuclear fusion begins at the core of the Sun. This is the nuclear reaction in which hydrogen atoms are converted to helium atoms plus energy. This energy (radiation) production prevents further contraction of the Sun.


Young stars often emit jets of intense radiation that heat the surrounding matter to the point at which it glows brightly. These narrowly-focused jets can be trillions of miles long and can travel at 500,000 miles per hour. These jets may be focused by the star's magnetic field.

Later, the Sun stabilizes and becomes a yellow dwarf, a main sequence star which will remain in this state for about 10 billion years. After that, the hydrogen fuel is depleted and the Sun begins to die.


From the Earth, our Milky Way Galaxy is visible as a milky band that stretches across the night sky.

Our Solar System is located in the outer reaches of the Milky Way Galaxy, which is a spiral galaxy. The Milky Way Galaxy contains roughly 200 billion stars. Most of these stars are not visible from Earth. Almost everything that we can see in the sky belongs to the Milky Way Galaxy.

The Sun is about 26,000 light-years from the center of the Milky Way Galaxy, which is about 80,000 to 120,000 light-years across (and less than 7,000 light-years thick). We are located on on one of its spiral arms, out towards the edge. It takes the sun (and our solar system) roughly 200-250 million years to orbit once around the Milky Way. In this orbit, we (and the rest of the Solar System) are traveling at a velocity of about 155 miles/sec (250 km/sec).To reach the center of the Milky Way Galaxy starting from the Earth, aim toward the constellation Sagittarius. If you were in a spacecraft, during the trip you would pass the stars in Sagittarius one by one (and many other stars).


Since we're inside the Milky Way Galaxy and we've never sent a spacecraft outside our galaxy, we have no photographs of the Milky Way Galaxy. Radio telescope data does, however, let us know a lot about it.

The arms of the Milky Way are named for the constellations that are seen in different directions. The major arms of the Milky Way Galaxy are the Perseus Arm, Sagittarius Arm, Centaurus Arm, and Cygnus Arm; our Solar System is in a minor arm called the Orion Spur.

The central hub (or central bulge) contains old stars and at least one black hole; younger stars are in the arms, along with dust and gas that form new stars.

The great rift is a series of dark, obscuring dust clouds in the Milky Way. These clouds stretch from the constellation Sagittarius to the constellation Cygnus.

The Milky Way Galaxy is just one galaxy in a group of galaxies called the Local Group. Within the Local Group, the Milky Way Galaxy is moving about 300 km/sec towards the constellation Virgo. Harlow Shapley (Nov. 2, 1885-Oct. 20, 1972), an American astronomer, was the first person to estimate the size of the Milky Way Galaxy, and our position in the galaxy (in 1918).


Origin of Solar System SUMMARY

CLICKER Question

QUESTION: Our Sun began emitting light:

a) when gravitational collapse occurredb) nuclear fusion reactions beganc) with rotation of the nebula d) with a supernova explosione) when Moon collided with Earth

The Planets

The Planets

The Planets

CLICKER Question

QUESTION: Which other planet has a near-Earth day?

a) Jupiterb) Venusc) Marsd) Mercurye) Pluto

Meteorites

http://www.britannica.com/eb/art-89387

Barringer Meteor Crater, AZ.35°02'N, 111°01'W; diameter: 1.186 kilometers (.737 miles); age: 49,000 years.

Geologic inventory of major impacts

IMPACT SITES

http://solarsystem.nasa.gov/multimedia/gallery/Chicxulub-browse.jpg

Chicxulub, Yucatan, MexicoN 21° 20’, W 89° 30'170 km diameter64.98 ± 0.05 million years

asteroid – A big rock or aggregation of rocks orbiting the Sunmeteoroid – A small rock orbiting the Sunmeteor – The visible light that occurs when a meteoroid passes through the Earth’s atmospheremeteorite – A rock existing on Earth that was once a meteoroid

http://www.amnh.org/rose/meteorite.html

Types of meteorites

http://piclib.nhm.ac.uk/meteorite-blog/image.php?src=http://www.nhm.ac.uk/nature-online/space/meteorites-dust/images/types-l.jpg&from=/meteorite-blog/

Stony meteorites are made from the same elements as terrestrial rocks: Si, O, Fe, Mg, Ca and Al. Like terrestrial rocks, stone meteorites are assemblages of minerals: pyroxene, olivine and plagioclase, but unlike terrestrial rocks, they also contain metal and sulphides.

Stony-iron meteorites have equal proportions of silicate minerals and iron-nickel metal. They are sub-divided into two major groups, mesosiderites and pallasites, which have very different origins and histories

Iron meteorites are dominantly composed of iron metal, generally with between 5 - 20 wt. % nickel. They are sub-divided into many different groups on the basis of trace element chemistry. They can also be sub- divided according to metallographic texture.

http://www.nhm.ac.uk/jdsml/research-curation/projects/metcat/bgmettypes.dsml

94%5% 1%

Meteorites

Stony Meteorites (94% of all falls)

CHONDRITES (97%) ACHONDRITES (3%)

Chondrites are the most abundant, have VERY PRIMITIVE CHEMISTRY with Ca and Al rich inclusions known as "CHONDRULES" (mm-sized "beads") thought to have condensed from gases in the solar nebula, and flecks of Ni and Fe metals.1. Carbonaceous -- 1% carbon in matrix

and organic compounds, including hydrocarbon chains and rings, and amino acids (outer asteroid belt)

2. Ordinary --the most numerous, comprising ~85% of all finds, with olivine, orthopyroxene mineralogy (middle asteroid belt)

3. Enstatite -- contain the mineral enstatite, a magnesium silicate (inner asteroid belt)

75 to 90% silicates + 10 to 25% Ni, Fe alloy

Achondrites underwent melting, and closely resemble EARTH ROCKS, collected mostly when seen to fall. They have little to NO METAL and NO CHONDRULES.

Microscopic view of a spherical chondrule, 1 millimeter in diameter. The bright, colored regions within its margins are mineral crystals. The black region between the crystals is glass and represents once-molten material. This chondrule is in Semarkona, an ordinary chondrite which fell in the Madhya Pradesh region of India.

http://meteorites.lpl.arizona.edu/chondrule.htmlhttp://www.meteorite.fr/en/classification/ordinarychon.htm

Types of meteorites

Meteorites

Iron Meteorites (5% of all falls)

These irons are alloys of nearly pure nickel and iron, and thus are very heavy compared to normal rocks. When cut and polished, the crystals are seen to form a distinctive criss-cross pattern of elongate crystals, known as a Widmanstätten pattern, which indicates slow cooling. Presumably, therefore, irons represent the fragments of the core of an asteroid or large ‘planetoid.’

http://tesla.jcu.edu.au/Schools/Earth/EA1004/Hazards/meteorites.html

Gibeon (IVA) iron meteorite, Gibeon, Namibia.

meteorites.wustl.edu/id/metal.htm

Types of meteorites

Meteorites

Stony-Iron Meteorites (1% of all falls)

Pallasites - named for the German naturalist Peter Simon Pallas; mixtures of metal and silicate material, in a complex network of green, yellow, or brown crystalline pods of olivine surrounded by a bright silver-colored iron-metal matrix.

50% silicates + 50% Ni, Fe alloy

The Brenham (Kansas) pallasite consists of olivine pods in a silver-colored iron-metal matrix.

http://meteorites.lpl.arizona.edu/composition.html

http://www.meteorite.fr/en/classification/stonyiron.htm

Types of meteorites

Meteorites

Origins of meteorites

Isotopic and chemical signatures indicate that most meteorites came from about 100 original asteroids.

The solar system condensed into dust particles and mm-sized balls called chondrules. Chondrules and dust were drawn together by gravity and formed the planets and the asteroids. Asteroids smashed by collisions formed chondrite meteoroids. These make up about 87% of all meteorites found.

Some asteroids were so large that radioactive elements (mainly Aluminium 26) heated and melted their cores. The heavier metals (iron and nickel) sank inward and the lighter stony material floated outward, differentiating the asteroid. When these asteroids were smashed by collisions, they formed three types of meteoroids. The cores formed iron meteoroids (4%), the core mantle boundary formed stony irons (1%) and the mantle and crust formed achondrite meteoroids (8%).

astronomy.neatherd.org/meteorites/families.htm

Meteorites

99.99% percent of all meteorites are of asteroidal origin.

Carbonaceous -- (outer asteroid belt)

Ordinary -- (middle asteroid belt)

Enstatite -- (inner asteroid belt)

CHONDRITES:

IRON:

Originate from M-type asteroids, and are thought to be core fragments of large asteroids shattered by impacts.

ASTEROIDAL


Meteorites


Meteorites

LUNAR MARTIAN

Chemical compositions, isotope ratios, minerals, and textures of the lunar meteorites are all similar to those of samples collected on the Moon during the Apollo missions. Taken together, these various characteristics are different from those of any other type of meteorite or terrestrial rock. For example, all of the meteorites that are classified as feldspathic breccias are rich in anorthite (plagioclase feldspar), mineralogically, and calcium aluminum silicate, chemically. That is, these meteorites have high concentrations of aluminum and calcium. Uniquely, the lunar highlands are composed predominantly of anorthite. Anorthite is much less common on asteroids and, to the best of our knowledge, on the surface of any other planet or planetary satellite.

Of the 24,000 or so meteorites that have been discovered on Earth, 34 have been identified as originating from the planet Mars. These rare meteorites created a stir when NASA announced in August 1996 that evidence of microfossils may be present in one of these Mars meteorites. The 34 Mars meteorites are divided into three rare groups of achondritic (stony) meteorites: shergottites (25), nakhlites (7), and chassignites (2). Consequently, Mars meteorites as a whole are sometimes referred to as the SNC group. They have isotope ratios that are said to be consistent with each other and inconsistent with the Earth.

CLICKER Question

QUESTION: Lunar and Martian meteorites are:

a) nickelb) pallasitesc) irond) chondritice) stony

Chaotian Eon

The Neochaotian began with the first light from the Sun. Its periods are the Hyperitian (the Titan Sun god Hyperion) for the time when gravitational collapse made the Sun’s first light brighter than its subsequent main sequence, followed by the Titanomachean (the war of Titans), to encompass the collision of proto-planets to form our present set of planets.

The Eochaotian began when the Solar Nebula became a closed system with respect to the rest of the giant molecular cloud and encompasses the agglomeration of the Solar System constituents from the nebula. It includes the Nephelean Period, for the cloud that is the nebula, and the Erebrean Period (Erebus, darkness) for the proto-Sun, yet to be luminous.

Proposed time scale by NASA scientists(Goldblatt et al., 2010)

Chaotian is Solar System wide

Early Earth

Proto-Earth “Tellus” original (“primordial”)atmosphere would have mostly been hydrogen and helium, like the gas giants. This atmosphere was lost due to a number of factors: • Its lower gravitational field (compared to gas giants) allowed escape of H and He • Solar wind stripped much of the atmosphere, until the magnetic field was established • Energy from planetesimal impacts would send some of the gas into space

Late Chaotian Earth

http://www.scientificamerican.com/slideshow.cfm?id=the-night-sky-will-fade-to-black

Early Earth

.Hephaestean for the lower Palaeohadean (Hephaestus, the Olympian god of fire and blacksmith for the gods), for an extreme silicate-water vapor greenhouse and a molten crust, which solidified in ~10My

Jacobian after Australia’s Jack Hills, which yield the earliest zircons.

Canadian, from crustal material dated back to 4.28 Ga is found in the Canadian Shield.

Procrustean (4.2 to 4.1 Ga) from Procrustes, whose bed fitted all life.

For the lower Neohadean period (4.1 to 4.0 Ga), we suggest Acastan, after the 4.03 Ga Acasta Gneiss.

Promethean, for the Late Heavy Bombardment, which would have vaporized the ocean and exterminated any pre-existing life; accordingly, we name the upper Neohadean period

Hadean EarthThe Hadean Eon begins after Theia (Proto-Moon) and Tellus (Proto-Earth) collided to form the Earth-Moon system. The Hadean is restricted to Earth’s geology, in contrast to the solar system wide Chaotian.

Goldblatt et al. (2010)

Early Earth

Habitability

Habitability

The red region is too warm, the blue region too cool, and the green region is just right for liquid water. Because it can be described in this way, sometimes it is referred to as the "Goldilocks Zone.”

Habitability

Our Solar System Habitable Zone has been recently redefined from 0.95 astronomical units (AU, or the distance between Earth and the sun) to 1.67 AU, to a new range of 0.99 AU to 1.7 AU.

Thus Earth is at the EDGE OF THE HABITABLE ZONE!

Habitability

“Faint Young Sun Paradox”

The problem:

CLICKER Question

QUESTION: The “Faint Young Sun Paradox” assumes that:

a) Earth was molten for billions of years in the pastb) Earth was frozen for billions of years in the pastc) Earth has always been at the same distance from Sun d) Sun was less luminous in the paste) Sun will become faint over the next billion years

Documents

Open Earth Systems: An Earth Science Course For Maryland Teacher Professional Development EARTH HISTORY AND THE FOSSIL RECORD DAY 1 - Weds. July 9 AM Instruction: