eng'g222 group1
TRANSCRIPT
Myths, theories, hypotheses
Creation
An immense of biological and geological change has occurred in a time span.
The age of the Earth is one-third of the age of the universe.
The process of plate tectonics has played a major role in the shaping the Earth’s oceans and continents, as well as the life they harbor.
The earth was formed by accretion from the solar nebula around 4.54 Ga(billion years ago).
Volcanic outgassing created the primordial atmosphere, but it contained almost no oxygen and would not support life.
A very large collision tilted the earth and formed the moon.
Much of the Earth was molten because of extreme volcanism and frequent collisions with other bodies.
The process of plate tectonics shaped the Earth's oceans and continents, as well as the life they harbor.
The biosphere had a significant effect on the atmosphere and other abiotic conditions such as the formation of the ozone layer, the proliferation of oxygen, and the creation of soil.
The Solar System was formed formed from a large rotating cloud of interstellar dust and gas of hydrogen and helium called the Solar Nebula.
It was created shortly after the Big Bang, 13.7 Ga and heavier elements formed the supernova.
About 4.5 Ga, the nebula had a contraction that triggered by the shock wave of the nearby supernova.
The shock wave made the nebula rotate and the cloud to accelerate which resulted to the flattening of the nebula to protoplanetary disk perpindicular to its axis of rotation.
Collisions of other large debris formed Protoplanets, orbiting the nebular center.
After more contraction, a T-Tauri star ignited and evolved into the sun.
Protoplanitary disk began separating into rings.
The process called Runaway Accretion successively clumped together larger fragments of dust and debris to form Planets.
Earth formed in this way about 4.54 Ga and was completed within 10-20 million years .
The proto-Earth grew by accretion until its interior was hot enough to melt the heavy, siderophile metals.
These metals sank due to higher densities resulted to the separation of a primitive mantle and a metallic core, 10 million years after the Earth’s formation.
The Earth’s first atmosphere was composed of light elements from solar nebula, mostly H and He.
Hadean Eon-the first eon in Earth’s History which begins in the Earths formation.
Archean Eon-followed from Hadean Eon at 3.8 Ga.
Giant Impact Hypothesis-the moon was formed.
Late Heavy Bombardment- a period of intense meteorite impacts that began about 4.1 -3.8 Ga, at the end of the Hadean.
Volcanism was severe due to the large heat and geothermal gradient.
By the beginning of the Archean, the Earth cooled significantly.
Life couldn’t survive due to lack of Oxygen and Ozone Layer.
The Giant Impact Hypothesis proposes that the Moon originated after a body the size of Mars struck the proto-Earth a glancing blow.
Theia-a former planet which had collided with the Earth.
The impact was enough to vaporize the Earth’s outer layers and melt both bodies.
Under the influence of its own gravity, the ejected material became a more spherical body: the Moon.
Legend:
yellow - Sun
blue - Earth
black - Theia
Mantle convection, the process that drives plate tectonics today, is a result of heat flow from the Earth's interior to the Earth's surface.
Involves the creation of rigid tectonic plates at mid-ocean ridges.
During the early Archean (about 3.0Ga) the mantle was 1600°C so the convection of the mantle was faster.
While a process similar to present day plate tectonics did occur.
The initial crust, formed when the Earth's surface first solidified.
However, it is thought that it was basaltic in composition, like today's oceanic crust, because little crustal differentiation had yet taken place.
The first larger pieces of continental crust, which is a product of differentiation of lighter elements that appeared at the end of the Hadean.
What is left of these first small continents are called cratons.
These pieces of late Hadean and Archean crust form the cores around which today’s continents grew.
Earth is often described as having had Three Atmospheres:
1) captured from the solar nebula, composed of solar wind and Earth’s heatgases rele
2) volatile gases released by molten Earth, gases ireleased by volcanoes, rich in greenhouse gases but poor in Oxygen.
3) rich in Oxygen
The new atmoshere probably contained water vapor, carbon dioxide, nitrogen, and smaller amounts of pther gases.
The ocean and atmosphere would therefore have started to form even as the Earth is formed.
The water must have been supplied by meteorites from the outer asteroid belt and some large planetary embryosfrom beyond 2.5 AU.
Comets may also have contributed.
Clouds formed as the planet cooled and rain created the oceans as early as 4.4 Ga.
The Proterozoic Eon lasted from 2.5 Ga – 542 Ma (million years ago).
Cratons grew into continents with modern sizes.
The change to an oxygen-rich atmosphere was a crucial development.
This eon saw a couple of severe ice ages called snowball Earth.
Lithified Stratomatolites on the shores of Lake Thetis, Western Australia
It is believed that oxygen was produced by the earliest cells.
During the Siderian Period(2500-2300 Ma), the oxidized iron, also called banded iron formations,formed abundantly and appeared as red as layer in geological strata.
The released oxygen was bound up with limestone, iron,and other minerals.
Oxygen finally began to accumulate the atmosphere.
Some oxygen was stimulated by incoming UV radiation to form ozone.
The ozone layer absorbs a significant amount of UV radiation that once had passed through the atmosphere.
A banded iron formation from 3.15 Ga Moories Group, Barberton Greenstone Belt, South Africa. Red layers represent the times when oxygen was available, gray layers were formed in anoxic circumstances.
Although the Sun’s luminousity increases 6% every billion years, the Earth did not get warmer.
Instead, geological record seems to suggest it cooled dramatically during the early Proterozoic.
The Ice Age(around 2.3 Ga) caused increased oxygen concentration and decreased methane(CH4) in the atmosphere.
A reconstruction of Pannotia (550 Ma)
Reconstruction of tectonic plate movement can be made reliably using fitting of continental margins, ocean floor, magnetic anomalies and magnetic poles.
Through the historyof the Earth, ther have been times when the continents collided and formed a supercontinent with later broke up to new continents.
Super continent RODINIA broke up and may formed supercontinent PANNOTIA or VENDIA.
The evidence for it is a phase of continental collision known as Pan-African Orogeny.
AFRICAN OROGENY-joined the continental masses of current-day Africa, South America, Antarctica and Australia.
GONDWANA-included most of the landmass now in the Southern Hemisphere, Arabian Peninsula, and the Indian Subcontinent.
LAURENTIA-equivalent to current-day North America.
The end of the Proterozoic saw at least two Snowball Earths that the oceans froze completely.
This happened about 716.5 and 635 Ma in the Cryogenian Period. (still under investigation)
During the Snowball Earths, most of the continental surface was covered with permafrost leading to the end of the glaciations.
Increased volcanic activity resulted from the break-up of Rodinia at about the same time.
The Phanerozoic is the major eon of life on Earth.
It consist of three eras: PALEOZOIC
MESOZOIC
CENOZOIC
The Paleozoic era (meaning: era of old life forms) was the first and longest era of the Phanerozoic eon, lasting from 542-551 Ma.
There were unexpected changes in the environment resulting from natural disasters.
The continents formed at the break-up of Pannotia and Rodinia would slowly move together again.
This resulted in phases of mountain building that created supercontinent PANGEA.
Pangea was a supercontinent that existed from about 300 to 180 Ma. The outlines of the modern continents and other landmasses are indicated on this map.
Pannotia had broken apart in the smaller continents:
LAURENTIA, BALTICA, SIBERIA and GONDWANA
-more oceanic crust is formed by volcanic activity
-the ocean floors and sea levels had risen
-large areas of the continents were below sea level
○ Laurentia and Baltica collided between 450-400 Ma to form LAURUSSIA (EURAMERICA).
-traces of the mountain belt which resulted from this collision can be found in Scandinavia, Scotland and the Northern Appalachians
○ Gondwana and Siberia began to move towards Laurussia.
Urulian Orogeny-collision of Siberia with Laurussia.
The collision of Gondwana and Siberia is called The Variscan or Hercynian Orogeny in Europe and Allegenian Orogeny in North America.
The Carboniferous period (359-299 Ma) the latter phase had taken place and resulted to the formation of the last continent.
The climates were warmer than today but at the end of Ordovician saw a short ice age which glaciers covered South Pole where the former Gondwana was situated.
Mesozoic (“middle life”) era lasted from 251-65.5 Ma.
It is sudivided into three periods: TRIASSIC, JURASSIC and CRETACEOUS
Began with Permian-Triassic extinction event Combination of volcanic event, an asteroid
impact, methane hydrate gasification, sea level fluctuations, and major anoxic event
Ended with the Cretaceous-Paleogene extinction event Wiped out dinosaurs(remains uncertain) 65 Ma, a 10 km (6.2 mi) asteroid struck the Earth just off
the Yucatán Peninsula where the Chicxulub crater is today.
The Cenozoic Era began at 65.6 Ma.
It is subdivided into the PALEOGENE and NEOGENE periods.
This is the era when they diversified into their modern forms.
Paleogene Neogene
Genesis 1:1: “In the beginning, God created the heavens and the earth.
Our universe, including our planet, Earth, was in existence for an indefinite time before the creative days began.
Geologists estimate that the Earth is 4 billion years old.
Astronomers calculate that the universe may be as much as 15 billion years old.
The Hebrew word translated “day” can mean various lengths of time not just 24-hour period.
“If I as a geologist were called upon to explain briefly our modern ideas of the origin of the earth and the development of life on it to a simple, pastoral people, such as the tribes to whom the Book of Genesis was addressed, I could hardly do better than follow rather closely much of the language of the first chapter of Genesis.”—Geologist Wallace Pratt.
Consists of a series of constant processes through which earth materials change from one form to another over time.
is a model that describes the formation, breakdown, and reformation of a rock as a result of sedimentary, igneous, and metamorphic processes.
is a general model that describes how various geological processes create, modify, and influence rocks.
Cementation- The process by which clastic sediment is lithified by precipitation of mineral cement, such as calcite cement, among the grains of the sediment.
Compaction- Tighter packing of sedimentary grains causing weak lithification and a decrease in porosity, usually from the weight of overlying sediment.
Deposition- The settling of materials out of a transporting medium.
Erosion- The processes that loosen sediment and move it from one place to another on Earth's surface. Agents of erosion include water, ice, wind, and gravity.
Pressure- The force per unit of area exerted upon something, such as on a surface.
Lithification- The processes by which sediment is converted into sedimentary rock. These processes include cementation and compaction.
Magma- Molten rock, generally a silicate melt with suspended crystals and dissolved gases.
Melting- To go from a solid state to a liquid state.
Metamorphism- Alteration of the minerals and textures of a rock by changes in temperature and pressure, and/or by a gain or loss of chemical components.
Sediment- Material (such as gravel, sand, mud, and lime) that is transported and deposited by wind, water, ice, or gravity; material that is precipitated from solution; deposits of organic origin (such as coal and coral reefs).
Transportation- The processes that carry sediment or other materials away from their point of origin. Transporting media include wind, water and mantle convection currents
Uplift-A structurally high area in the crust, produced by movements that raise the rocks, as in a broad dome or arch.
Weathering- The processes by which rocks are chemically altered or physically broken into fragments as a result of exposure to atmospheric agents and the pressures and temperatures at or near Earth's surface, with little or no transportation of the loosened or altered materials.
This image shows how James Hutton first envisioned the rock cycle.
James Hutton (mid-1700’s)-promoted uniformitarianism: processes that occur today are the same ones that occurred in the past to create the landscape and rocks as we see them now.
He observed rocks from a nearby river from his house.
As shown in the diagram above, Hutton first conceived of the rock cycle as a process driven by earth’s internal heat engine.
Heat caused sediments deposited in basins to be converted to rock, heat caused the uplift of mountain ranges, and heat contributed in part to the weathering of rock.
Magma rises from deep inside the Earth.
Some are trapped underground and hardens into intrusive igneous rock.
Some erupts on the surface of the Earth as extrusive igneous rock.
Pressure and heat from below cook or metamorphose the rocks, colliding continents to push them up to the surface.
Wind, rain, ice and gravity erode the rock and carry away sediment.
Rivers deposit it along their flood plains or at the bottom of lakes and seas, where it builds up in layers and hardens under pressure into sedimentary rocks.
These sink into the ground and are metamorphosed by head and pressure, or folded and uplifted again by more tectonic activity, continuing the cycle.
The rock cycle is powered from above and below. Heat from within the earth ultimately derived from radioactive
decay and the slow solidification of the inner core causes the upwelling of intrusive and extrusive rocks and produces the process of metamorphism of rocks.
It also drives the drifting continents, uplifting mountain ranges. The energy of the Sun heats and expands rocks at the surface and
ultimately drives the wind, waves and precipitation that cause erosion. Gravity causes landslides which contribute to the circulations of rocks.
This picture shows a basaltic eruption of Pu'u O'o, on the flanks of the Kilauea volcano in Hawaii. The red material is molten lava, which turns black as it cools and crystallizes.
Photograph from space of the Mississippi Delta. The brown color shows the river sediments and where they are being deposited in the Gulf of Mexico.
The Grand Canyon is famous for its exposures of great thicknesses of sedimentary rocks.
http://www.visionlearning.com/library/module_viewer.php?mid=128
http://imnh.isu.edu/digitalatlas/geo/basics/diagrams.htm
http://destinationofmarvel.blogspot.com/2010/09/rock-cycle.html
http://wol.jw.org/en/wol/d/r1/lp-e/1200001558#s=2:0-3:332
http://destinationofmarvel.blogspot.com/
http://encyclopedia.thefreedictionary.com/earth%27s+history
B.S. Environmental and Sanitary EngineeringA.Y.: 2012-2013
Second Semester
Eng’g222: Engineering GeologyTopic No.1: THE EARTH’S HISTORY AND THE ROCK CYCLE
GROUP I:
Alarcon, Arjay, BSESE 2A
Avila, Joshua, BSESE 2A
Maristela, Stephen G., BSESE 2A
Borromeo, Donna Gift C. BSSE 1-Irr.
Eng’r. Iglesia (Instructor)
November 07, 2012
Wednesday-1:00-3:00pm
GR-1