2004 Final Section 3&4 Q&A

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Earth & Planetary Sciences
EPSC 201
Anthony Williams- Jones

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 samples. 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 plate trajectories. Hot spots don’t exist forever. They come and go over a time period of tens of millions of years. 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 building blocks. 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 Albite K-Feldspar 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 Anorthite 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
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