Evolution of the EarthThe First Billion YearsThe Earth is a Unique Planet1. Earth remains geologically active on its own internal energy source after 4.0 billion years of history. Seen today in earthquakes (16,500/year greater than 4.0) , volcanoes (4-500 active now or in the recent past), and the building of mountains (Mt. Everest is still rising about an inch a year).The Earth is a unique planet2. Surface temperature allows liquid water to exist, even though the energy the Earth receives from sun the has increased 30% in past 4 billion years. Surface temperatures should be a couple of hundred degrees above what they are today. Something is actively regulating the temperature.Unique things about the Earth we need to explainIn contrast, temperatures on Venus are about 900 F, on Mars about –193 F, on Jupiter –243 F, and on Saturn –301 F.http://www.shef.ac.uk/physics/people/vdhillon/teaching/phy213/phy213_lowmass.htmlhttp://www.cosmographica.com/gallery/portfolio/portfolio151/pages/172-RedGiantSun.htmAn artist’s Vision of the Red Giant phase of the sun about 4 billion years in the future.2. Surface temperature allows liquid water to exist, even though the energy the Earth receives from sun the has increased 30% in past 4 billion years. Surface temperatures should be a couple of hundred degrees above what they are today. Something is actively regulating the temperature.Unique things about the Earth we need to explainIn contrast, temperatures on Venus are about 900 F, on Mars about –193 F, on Jupiter –243 F, and on Saturn –301 F.3. Earth has abundant life., What is more this life has increased in complexity, diversity, and abundance with time. Meanwhile life has adapted to most extremes of the earth’s environments, such as 1 1/2 times the boiling point of water, 50obelow zero, 2 miles below ground, and, more remarkably, normal conditions.Unique things about the Earth we need to explain4. The atmosphere is oxygen rich even though oxygen is extremely chemically reactive. Left alone all oxygen would disappear in less than 1000 years. Something is actively maintaining an oxygen rich atmosphere.Unique things about the Earth we need to explainHydrogen 75%Helium 25%Methane (CH4) traceAmmonia (NH3) traceWater ice traceC02 95.3%Nitrogen 2.7%Argon 1.6%Oxygen 0.15%Water vapor 0.03%Saturn MarsNitrogen 79%Oxygen 19%C02 0.03%Argon 1.0%Water vapor variableEarth5. A crust with two distinct divisions – continents and ocean basinsUnique things about the Earth we need to explainIn contrast, nearly 90% of Venus' surface appears to consist of recently-solidified basalt lava. Mars, despite evidence for sedimentary rocks, is also mostly basaltic in compositionThe Earth is a Unique Planet• What can we learn from the Earth’s past that will help us understand the present and the future?The questions . . .• We want to look at the norm, and at the extremes – what is the Earth capable of?• Many of these are at time scales longer than humans have experienced or can imagine.• But, right now we are not so much about narrowly human concerns, but about how this planet, our home, lives and behaves.4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.04.5Archaean ProterozoicPhaneroGrenvilleJust How Long is Earth History ?And When Did the Important Things Happen ?HadeanBillions of YearsOldestRocksOrigin of ContinentsOrigin ofEarth4.5-4.0Plate Tectonic ProcessesFirst RecordOf liquid WaterThe First Half Billion Years4.5 — 4.0Originshttp://www-curator.jsc.nasa.gov/outreach1/expmetmys/slide set/Slides16-20.htmThe solar system began as a spinning cloud of gas and dust, called the solar nebula, which collapsed under its own weight to form a new star, our Sun. As the solar nebula spun and churned, dust grains stuck together to form dustballs, and huge bolts of lightning melted them into small spheres. These solidified into rocky balls called chondrules. (Painting by Don Dixon, NASA JSC photo S76-25001) Click for web site for description of solar system formationThe Solar Nebulahttp://www.howardastro.org/documents/HET607Essay.htmEmbryonic planets emerge from the chaos of the protoplanetary disk. They endured constant bombardment by a progression of ever-larger objects.http://www.psrd.hawaii.edu/Feb08/EarthMoonFormation.htmlhttp://www.lpi.usra.edu/education/timeline/gallery/slide_10.htmlFormation of the Earth-Moon SystemA Mars-sized planet collided with Earth, vaporizing, melting, and throwing debris from the impactor and Earth's outer layer into orbit around Earth, creating an encircling debris ringAt ~4.5 Ga the Earth-Moon collision provided enough energy to melt them and begin their physical evolution.~ 4.5 Ga ~ 4.5 Ga ~ 4.5 GaThe Moon as seen from Earthhttp://www.psi.edu/hartmann/pic-cat/images/72.jpghttp://www.psi.edu/hartmann/pic-cat/images/72.jpgEarly Earth From the Moon About 4.4 billion years agoAt ~4.3 GA the Earth-Moon system reach this stage. The Earth is already stratified by density, convection cells are operating, and tectonic processes have begun.~ 4.3 Ga ~ 4.3 Ga ~ 4.3 GaBecause the moon was so close the tides were immenseThe moon as it appears todayThe moon as it might have appeared at 4.0Formation of the First Solid Ground~ 4.0http://www.space-art.co.uk/pages-en/debris/Bombardment.htmEarth About 4.4 billion years ago~ 4.4 Ga ~ 4.4 Ga ~ 4.4 GaStill molten hot, without water or life, being bombarded continuously by meteorites.http://www.flickr.com/photos/killbyte/318021281/Earth About 4.4 billion years ago~ 4.4 Ga ~ 4.4 Ga ~ 4.4 GaMolten hot, without water or life, surface just beginning to solidify, being bombarded continuously by meteorites.http://www.gps.caltech.edu/~mjwillis/research/bugbuster.htmlEarth About 4.2 billion years ago~ 4.2 Ga ~ 4.2 Ga ~ 4.2 GaStill molten hot, without water or life, being bombarded continuously by meteorites.http://mysite.wanadoo-members.co.uk/mearca/pictures.htmEarth About 4.2 Billion Years Ago~ 4.2 Ga ~ 4.2 Ga ~ 4.2 Gahttp://www.arcadiastreet.com/cgvistas/earth_010.htmEarth About 4.1 Billion Years AgoStill too hot for water, or life~ 4.1 Ga ~ 4.1 Ga ~ 4.1 GaSince the moon and the Earth had a conjoined origin they started out with nearly identical compositions and appearances.http://www.nightskyobserver.com/images.htmThis means they both were composed of anorthosite (Ca plagioclase) and the mafic(basaltic) parent rock.Anorthosite Ca plagioclase