ES 10 - Midterm Review

Lisa Tauxe

Topics Covered:

Study: Introduction of the Blue Planet, notes from lecture 1, and read this link:

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 3.

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.

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 carefully.
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 explosiions.
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 3

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.
Earthquakes

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 moho.
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 lecture 3, lecture 11.

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 from lecture 4, lecture 5, lecture 6.

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 viscous).
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:

Study: Chapter 5, notes from lecture 7 and links therein.

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 10.