0 Vocabulary tendencies differentiation rotating supernova cloud of gas/dust asteroid cloud of gas/dust gravity dense solar nebula planets accretion planetessimal protoplanets meteors moon rotation wobble gneiss tectonic plates (L. tectonicus, pertaining to building, ) hyperthermophiles density magnetic field biosphere Hadean THE STORY OF EARTH S FORMATION The shock cord (bungee) cord is 10 meters in length. Scale: 10 meters = 3.0 billion years Images for the Earth Story Line include: E-1 Solar System Formation (at beginning of rope) E-2 Accretion (1.33 meters from beginning) E-3A Volcanoes (1.5 meters from beginning) E-3B Rivers of Lava (Same as E3A) E-4 Moon Formation (1.66 meters from the beginning) E-5A Liquid Inner/Solid Outer Core (3 meters from beginning) E-5B Solid Crust (Same as E5A) E-6 Liquid Water (3.3 meters from beginning) E-7 Acasta Gneiss - first rock (3.3 meters from beginning) E-8 Tectonic Plates (3.3 meters from beginning) E-9 First Life (3.66 meters from beginning) E-10 Magnetic Field (4.66 meters from beginning) E-11 Oceans (5.0 meters from beginning) E-12 Biosphere (end of rope) 1-1 Prior to beginning the presentation: Set up the Earth Story Rope in a circle or spiral and place these cards for each event at their appropriate place along with any demonstration for the events. Lay out Home Page rope and pictures. Presentation: Pointing to the Home Page rope, Do you remember when we told this story? Now we are going to stretch out the part from the Supernova to the appearance of our home planet, Earth. On the Earth Story Rope each step I take is equal to 300 million years. The Story... Light a candle. Mystery is always at work in the Universe. The Universe tells its story through this mystery. However, not everything is mysterious because the Universe has given us some clues. The most important clues it gives us are the tendencies that rule everything that occurs in the Universe. One of those tendencies is Differentiation. Everything changes. In the beginning there was only hydrogen now there are planets, rocks, oceans, giraffes and you and me.
1-2 Differentiation was at work when mystery came out of the darkness some 5 bya. It all started with a supernova explosion. A supernova begins when the outer layers of a star rush inward under a lot of pressure until it gets very very hot and explodes releasing elements heavier than iron and blasting them into space. E-1 Solar System began to form (5 bya) Squeeze the cloud Demonstration The space between stars is not empty. It contains clouds of gas and dust. A new solar system began to form when a supernova explosion disturbed a rotating cloud of gas and dust. This rotating cloud of gas and dust was not like the clouds we see in the sky, it was a cloud that contained mystery itself. Out of that mystery came our sun and its eight planets, Mercury, Venus, Earth, Mars, Jupiter, Saturn, and Neptune. Not only that -- it also created, asteroids and other huge masses of rock and fire. This is the story of how solar system gave birth to the Earth. The supernova explosion made waves in space that squeezed the cloud of gas and dust. Just like a dancer that spins faster as she pulls in her arms, the cloud began to spin as it collapsed. Eventually, the cloud grew hotter and denser in the centre. It got so hot that it became a star, our Sun. 1-3 Pull out planetessimals The planets were born in the swirling currents of this great cloud of gas and dust. Planets near the sun Mercury, Venus, Earth and Mars evolved as globes of rock. They were too small and their gravitational fields too weak to capture and hold the gases from the nebula. Far from the sun the massive planets Jupiter and Saturn with huge gravitational fields, did attract and hold thick gaseous atmospheres of hydrogen and helium
2 As the disk got thinner and thinner, particles began to stick together and form clumps. This is known as accretion. Some clumps got bigger, as particles and small clumps stuck to them, eventually forming planetessimals and then planets or moons. E-2 Accretion (4.6 bya) 3 The early Earth was very violent. It was constantly bombarded by meteors that broke through the crust as it was trying to form. The hot insides of the Earth came up in the form of volcanoes. These volcanoes created rivers of lava that eventually hardened to form the crust. Scientists call it the Hadean Era (from the Greek God of the Underworld - Hades) Millions of years later the hot air rising off the surface of the new Earth will reach the cold atmosphere and will come back as rain -- water will form on the surface of our early Earth. E-3A Volcanoes E-3B Lava Flow
4 Demonstrate process with two spheres of clay, joining them together, breaking off bits and rejoining. E-4 Formation of Moon Demonstrate with knitting needle through centre of Earth. About 4.5 bya, following the cosmic laws of the universe, a large planetessimal pulled by gravitational forces hurled its way toward Earth. The object that collided with the Earth was about the same size as Mars. It broke through the hot crust of the Earth and then joined the Earth, splattering bits of the Earth s crust into space. These little bits, over time, came together through accretion and formed our moon. However, the moon was not as far away as it is today. When it first formed it was only 24,000 kilometres. Since it was so close, the Earth spun faster than it now does and one day was only 5 hours long. Today the distance to the moon is 385,000 kilometres. How many hours are there in a day now? The impact that formed the moon also caused the Earth to develop the perfect angle of rotation so that we have just the right amount of summer, winter, spring and autumn. You might say that the Earth and moon love each other very much as together they help balance life on Earth. The early Earth wobbled just like a baby when it first begins to walk. The moon s love for the Earth also helped the young Earth stop the wobbling and become more stable. The gravity of the moon provides another gift for the Earth. It controls the ocean tides. Without the moon the Earth would have flooded soon after it was born. 5 Demonstrate with ping pong balls buried in sand and rocks on top. Shake to see heavy elements fall and lighter one rise. The surface of the Earth was still oceans of lava. The heaviest particles in the lava -iron and nickel- began to sink towards the centre, forming an inner and outer core. This process is still going on today. Eventually the surface began to cool as the Earth spun in cold space. And 400 million years after the moon formation the period of the great bombardment of particles ends and the Earth recovers enough from to have its first solid crust E-5A Inner/Outer Core E-5B Crust (4.1 bya)
6 Comet prop - we bought one at a good toy store. The Earth s atmosphere was full of hot and heavy clouds from the volcanoes. As the Earth cooled liquid water was able to form on the surface. Scientists tell us that comets of ice brought frozen water to the Earth some Comets were big enough to create giant lakes. E-6 Water begins to form on surface (4 bya) 7 Some of the oldest rocks in the world are found in Northern Canada. These metamorphic rocks were formed around 4 billion years ago by the immense heat and pressure inside the Earth. They are known as Acasta Gneiss (nice). E-7 First Rocks (4 bya) Samples of old rocks
8 E-8 Tectonic Plates (4 bya) Demonstrate by cracking a hard boiled egg and riding the bits over the egg surface Exactly when plate tectonics began is not known. We do know that it had to begin sometime close to the formation of the first rocks. What are plate tectonics? The outer part of the Earth is broken into sections like this eggshell that is cracked. The egg can be seen as a tiny model of the Earth. The thin shell represents the Earth s crust, divided into plates. Within the shell is a firm but slippery mantle. When I move the pieces of shell around, notice how the shell buckles in some places and exposes mantle in other places. The same thing happens on Earth, but on Earth, this activity results in the formation of mountains, earthquakes, and new ocean floor. The Earth s oceans and continents ride on tectonic plates that move slowly (centimetres per year) across the Earth s surface. The oceanic crust is constantly being formed or destroyed at when it meets the continental plates. The continental crust survives although greatly changed by the forces of plate tectonics. [In geology, a plate is a large slab of rock, while tectonics is a word of Greek origin meaning to build. ] 9 We do not know exactly when life appeared on Earth. It was probably around 3.9 billion years ago. We do know that some tube worms live in cracks on the floor of the ocean. They get energy from archea bacteria that can live at very hot temperatures above 90 C. These bacteria may have been the first forms of life on Earth and are called hyperthermophiles. E-9 First Life (3.9 bya)
10 As the inner and outer core built up its density the liquid metal iron core creates a magnetic field. The Earth s magnetic field protects life on Earth from dangerous particles. If planets did not have magnetic fields, life would be impossible. This core and the rotation of the Earth created a magnetic field. E-10 Magnetic Field (3.6 bya) Demonstrate magnetic field with iron filings sprinkled onto white paper over magnet. (We use a shallow box with a strong magnet taped to the bottom and the paper taped over the top of the box so you can not see the magnet.) 11 As the Earth continued to cool from its hot beginnings great masses of water formed all over the planet. We call these masses of water, oceans. E-11 First oceans (4 bya)
12 Creativity advanced further. By 2 billion years ago the Earth formed an atmosphere with oxygen. Now the hydrosphere, atmosphere and geosphere worked together with the sun s energy to create the Biosphere. If you were looking at the Earth from space, it might resemble what it looks like today. E-12 Bioshpere (2 bya)