Download 1-1 Prior to beginning the presentation: Set up the Earth Story Rope

THE STORY OF EARTH’S FORMATION
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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
1-1
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)
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)
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.
Squeeze the
“cloud”
The supernova explosion made waves in space that squeezed the cloud
of gas and dust.
Demonstration
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.
5
Demonstrate with
ping pong balls
buried in sand and
rocks on top. Shake
to see heavy elements fall and
lighter one rise.
E-5A Inner/Outer
Core
E-5B Crust
(4.1 bya)
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.
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
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
E-7 First Rocks
(4 bya)
Samples of old
rocks
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).
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
E-9 First Life
(3.9 bya)
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.
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
E-11 First
oceans
(4 bya)
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.
12
E-12 Bioshpere
(2 bya)
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.