Geology: Plate Boundaries, Plate Motion, Minerals, and Rocks, Study notes of Geology

Download Geology: Plate Boundaries, Plate Motion, Minerals, and Rocks and more Study notes Geology in PDF only on Docsity! Geology 04/09/2008 16:02:00 ← Figure 4.17, pg 101. ← Figure 4.18, pg 102. ← ← Plate Boundaries (4): Passive  The Plates are not actually interacting.  Figure 4.3, pg 89  Single most important plate boundary there is. ← ← Plate Motion  Wegner’s problem: Demonstrating motion o Movements are = 3-10 cm per year.  Easy enough to measure now, but impossible even as late as 1960’s. o Physical surveying over short distances. o Global Positioning Satellites using atomic clocks. ← Figure 4.30, pg 114. ← ← Triple Junctions  Interactions with three plates meet. ← ← Hot Spots  Not all volcanoes are at plate boundaries. o Plumes of very hot molten rock burn holes in the crust. ← ← Volcanic Island to Seamount (pg 457 & 105) ← ← What drives plate motion?  The heat escaping from the core is causing the mantle to convect. ← ← Slab-pull or Ridge-push? ← The Earth is Made of Rocks…. ← ← Electrons + Protons + Neutrons = Atoms  Electrons are negatively charged  Protons are positively charged  Neutrons are uncharged  Simplest atoms are: Hydrogen and Helium. ← ← Ions & Isotopes  When an atom gains or loses electrons it becomes an ion. o Cations have a positive charge o Anions have a negative charge  For Many common mineral, colors are variable ← ← Luster  The “quality” of light reflected from a mineral surface o A subjective comparison  Terms include vitreous, earthy, resinous, greasy, etc.  Major distinction: Metallic vs. Non-metallic Luster ← ← Streak  The color of the powdered mineral o More characteristic than the color of the bulk sample. o Determined by rubbing mineral on streak plate  Metallic minerals: black or dark-colored  Soft, non-metallic minerals: white or light-colored  Hard metallic minerals: none ← ← Cleavage/Fracture  The way a mineral breaks o A visible insight into the atomic arrangement  Cleavage: consistent, repeating, systematic o Halite: 3 planes of cleavage at 90 degrees to each other. o Calcite: 3 planes of cleavage not at 90 degrees to each other.  Fracture: Inconsistent, random o Quartz: curved surfaces (conchoidal) ← ← Hardness  Resistance to scratching o Uses scale developed in 1822 by Friedrich Mohs (pg 132) ← ← Mnemonic Devices  Memory tricks o The Girls Can Flirt And Other Queer Things Can Do ← ← Specific Gravity  A unitless measure of a mineral’s density. o Helps minimize the effect of irregular sample sizes  Ratio of mineral density to density of equal volume of water. o Quartz, feldspar = 2.7 o Galena = 7.5 o Gold = 19.3 ← ← Mineral Classification  There are more than 4000 identified minerals o 25 to 50 ones described each year  How do we go about organizing our knowledge? o Classify minerals based on chemical or structural aspects ← ← Chemical Classification  Group minerals by the elements they contain  Example: minerals that contain lead o Galena: PbS o Anlesite o Cerussite o Vanadinite ← ← Structural Classification  Group minerals by their atomic arrangements  Eample: Minerals with NaCl arrangement o Halite: NaCl o Galena: PbS o Sylvite: KCL o Claushalite: PbSe ← Melting Rocks  Subsurface melts (magma) form by melting existing rocks o There is no great underground reservoir of magma!  Melting occurs when: o Pressure is lowered on hot rock (decompression melting) o Water is added to hot rock (flux melting) o Rock is heated by other melts (thermal transfer melting) ← Page 83. ← Factors Affecting Melting Temperatures ← ← Magma Composition  Depends on the types of rocks that melt o Different minerals melt at different temperatures  What gets added along the way o Contamination by and assimilation of surrounding rocks o Merging with other magmas  What drops along the way o Fractional crystallization ← ← Contamination and Assimilation—page 159 ← ← Xenoliths—literally foreign rocks  Found in intrusive and extrusive rocks. ← Mixing—page 88 ← Partial Melting and Fractional Crystallization  Are two sides of the same phenomenon  Page 159 ← Bowen’s reaction series  Page 160 ← The Palisades  Page 86 ← ← Extrusive Forms  Lava flows—melt that reaches the surface  Tephra—melt that solidifies into fine particles o May fall from clouds or travel along the ground ← ← Intrusive Forms  Sill—tabular body intruded between layers of rocks  Dike—tabular body intruded across layers of rock  Batholith & stock—irregular bodies intruded across layers of rock  Laccolith—irregular body that bends up layers of rock ← ← Igneous rock classification  Based on the rock texture and composition  Texture is the type and relationship of the grains within the rock.  Composition based on chemistry or mineral content. ← ← Porphyritic Rocks  A mixture of grain sizes  Large grains are phenocrysts surrounded by finer-grained groundmass o May be phaneritic-porphyritic or aphanitic-porphyritic ← ← Igenous Rocks & plate techtonics  The basic relationship was clear early on o Volcanoes and plate boundaries  How do they relate at a deeper level? o Rock chemistry o Melt origins o Intrusive and extrusive features ← ← Sedimentary Rocks  Made of pieces of pre-existing rocks o Pore filled with air and water  And about 50% solids o Regolith (weathered rock) and humus (organic debris) ← ← Factors controlling Soil Development  Underlayment composition  Climate  Typography  Organisms  Time ← ← Paleosols  Literally, ancient soils o Once exposed at the surface, now buried. ← ← Sediment types  Detrital (clastic): Physically transported o Siliciclastic sediments made of silicate mineral fragments o Bioclastic sediments made of fragments of organisms  Chemical: Transported in solution o May end up as a chemical or biological sediment ← ← ← 04/09/2008 16:02:00 ← 04/09/2008 16:02:00 ←