EPSC201 2004 Final Exam Review Section 3&4
1. Using a sketch, describe the formation of the Hawaiian islands?
Hot spots – stationary
Plate – dynamic
This causes lines of islands to be formed. This
can tell you the past movement of the plates,
and how it changed direction if the line
segments change directions.
You can also tell how fast the plates are
moving, by looking at the spacing in between
the islands and the age of the islands by rock
India deﬁnitely went over a hot spot while it
was migrating north. We know this by identical
rocks found at the hot spot and rocks in India.
The hot spots give a lot of information about
Hot spots don’t exist forever. They come and
go over a time period of tens of millions of
2. Explain the statement “Silicate minerals comprise covalent and ionic bonds.”
The size of an ion has a big effect on the geometry of elements.
• Ionic Bonds – the transfer of electrons from one atom to another, which forms charged ions.
• Covalent Bonds – the bond shares electrons between the atoms, to ﬁll the outer shell of each
atom, making it stable. The bonds are much stronger then ionic bonds.
Most rocks are formed through silicate mineral in which silicon bonding to oxygen is one of the key
In the simplest form, silicon is bonded to four oxygens in the form of a tetrahedron through covalent
bonding. What we see in the diagram is an arrangement of silicon tetrahedron. If you add up all the
charges of silicon and oxygen, you end up with -4 (SiO 4). (Si has charge of +4, oxygen has charge of -2) 3. Relate the molecular structures of quartz and potassium feldspar.
Relationship of Quartz structure
to Feldspar Structure
Imagine four SiO molecules 4 x SiO = Si O
2 2 4 8
Substitute Al 3+ for Si4+in one of these molecules
SiO + AlO + SiO + SiO = AlSi O -
2 2 2 2 3 8
Add Na or K to supply missing charge = NaAlSi O or KAlSi O3 8 3 8
SiO + AlO + AlO + SiO = Al Si O 2-
2 2 2 2 2 2 8
Add Ca 2+ to supply missing charge = CaAl Si O 2 2 8
4. Name a volcanic and an intrusive igneous rock, and explain how you would
distinguish them based on appearance and mineral composition.
Igneous Rocks – igneous means ﬁre. These rocks originate from hot molten material. Basalt is an
example of igneous rock because it formed from lava ﬂowing out of the earth. Granite is also an igneous
rock. These rocks are formed from a liquid (magma). The process of forming a rock from a liquid is called
crystallization. These crystals clump together to make rocks.
Volcanic –ﬁne grained igneous rocks caused by rapid cooling. Not enough time to form large
crystals because the lava cools quickly.
Intrusive – plutonic, magma stays below the earths surface
5. Explain decompression m