ES 10 - Midterm Review
Elements of the Scientific
- forming a hypothesis
- testing the hypothesis
- formation of a theory
- formation of a law
- continual reexamination
Study: Introduction of the Blue
Planet, notes from lecture
1, and read this link:
Origin of the Universe
- Big Bang - 15 billion years ago
- The first atoms (75% hydrogen and
25% helium) formed in first 3 minutes.
- Gravitaion caused matter (H and
He) in the universe clumped to form stars. The law of gravitation states
that every body in the Universe attracts every other body.
- stars are big enough that the temperature
in the core allows "burning" of H to form He by nuclear fusion.
- larger stars have cores hot enough
to make elements up to the mass of iron
- elements heavier than iron are
all made in the violent death of exceptionally large stars - a phenomenon
known as asupernova explosion.
- by the way, an "element"
in the chemical sense is a fundamental substance into which matter can
be separated by chemical means.
Study: Chapter 2 of the Blue Planet,
notes from lecture
2 and lecture
Birth of the
- Ancient astronomers believed that
the entire Universe revolved around the Earth . this Earth-centered view
is called a geocentric astronomical system.
- Biblical scholars estimated the
age of the Earth (by counting back generations) to be some 6000 years old.
What we now believe based on scientific
- Just by looking around him, it
is possible to deduce that the Earth must be very old. He used the principle
of Uniformitarianism to translate his observations of the length of time
erosiona and weathering take now to realize that it must have taken a long
time to form the landscape he observed - read the Introduction in the book
- 4.6 Billion years ago a gas cloud
called a solar nebula collapsed to form our sun, and the nine planets in
our solar system.
- Our sun is an averaged sized star
that is in its hydrogen burning stage of evolution, is in the main sequence
and has another 4 billion years left to live. Virtually all the elements
in the sun that are heavier than helium were made in earlier supernova
- The inner four planets (Mercury,
Venus, Earth, Mars) are rocky and are called the terrestrial planets.
- There is a belt of large (up to
100 km sized) chunks of planetary material called the asteroid belt that
separates the terrestrial planets from the outer five planets.
- The first four of these (Jupiter,
Saturn, Uranus and Neptune) are huge balls of gas.
- The outermost planet (Pluto) is
rocky, small (and really cold).
Study: Chapter 1, notes from lecture
of the Earth
- The Earth is about 150,000,000
km from the Sun.
- It is about 13,000 km in diameter
and has a density about 5.5 times that of water.
- The average density of rocks in
the outer layer we live on is about 3 times that of water, so the Earth
has a very dense core.
- From study of meterorites thought
to be pieces left over from the original solar nebula, we infer that the
Earth has a core that is made of iron and nickel.
- generate sound waves that travel
through the earth.
- The point on the surface of the
Earth above the earthquake is called the "epicenter".
- There are two kinds of these "body
waves": compressional and shear.
- Earthquakes are measured using
"seismographs" (also known as seismometers).
- The Richter scale is used to calculate
the amount of energy releaced during an earthquake. Each step is an order
of magnitude so the energy released in a magnitude 4 earthquake is 10 times
larger than that released in a magnitude 3 earthquake.
- From the study of earth quakes
we see that shear waves do not travel through the outer core. Shear waves
cannot travel through liquids and this is the key evidence that he earth's
outer core is liquid. Other more subtle evidence suggests that it has a
small solid inner core.
- Between the thin crust (average
of about 30 km) that we live on and the core (about 3000 km down) is the
rocky mantle. The seismic feature that separates the crust from the mantle
is known as the Mohorovicic discontinuity, or the M-discontinuity, or the
- Convection in the Earth's liquid
outer core which is made of the conducting metals iron and nickel is the
source of the Earth's huge magnetic field.
- The Earth's magnetic field is similar
to that of a bar magnetic at the center of the Earth.
- The Earth's gravity field shows
that the crust is more or less in "balance". Larger objects (like
mountains) sink down into the mantle in a principle known as isostacy.
Study: Chapter 3 and notes from
the Earth Works
- Be familiar with Wegener's ideas
(beginning Chapter 6).
- Why were these not accepted?
- There are three types of plate
boundaries: convergent, divergent, transform. Convergent margins come in
two flavors: those in which one plate is subducted under another and one
in which two continents collide. Study the different styles at each type
of plate boundary and be able to draw cross sections (look at Figure 6.11).
Study: Chapter 6 and review notes
- Volcanoes are the way that the
Earth loses heat. They are the "sweat" of the Earth.
- Most volcanoes occur at divergent
plate margins, but some occur within plates (i.e. Hawaii).These are called
hot spots. Volcanoes are formed when molten rock (magma) comes out onto
the Earth's surface as lava.
- The viscosity (stickyness) of magma
is determined by temperature (the hotter it is, the less viscous (the more
"runny"), and the amount of silica (the more silica, the more
- There are three distinct types
of magma that differ in the amount of silica in them: basalt (only 50%),
andesite (60%), and rhyolite (70%).
- magmas also contain dissolved gases.
These are important because:
- some of them are "green house"
gases that can influence climate
- the faster gas bubbles out of the
magma, the more violent the eruption.
Study: Chapter 5, notes from
lecture 7 and links therein.
The Rock Cycle
- A mineral is nay naturally formed,
solid chemical element or chemical compound having a definite composition
and a characteristic crystal structure.
- Common minerals are the silicates:
formed from the silicate ion (a tetrahedral ion composed of silicon and
oxygen), the oxides: formed from oxygen, sulfides, carbonates and metals.
- Rocks are aggregates of minerals.
- There are three major types of
rocks: sedimentary, igneous and metamorphic.
- These form one from the other in
what is known as the rock cycle.
Study: Chapter 4 and notes from
lecture 9 and lecture