GEOL 101 1nd Edition Lecture 4 Outline of Last Lecture I Geologic Time II Scientific Method of Inquiry III Earth s Internal Structure Outline of Current Lecture I Dynamic Earth II Minerals as Building Blocks III Physical Properties of Minerals Current Lecture Introduction to Plates Tectonics The theory that continents move around on the surface which was also called continental drif It took about 50 years for this to be accepted as a theory This theory gives an explanation and a model of the Earth s lithosphere which is a thin layer broken up into pieces or plates When talking about plate boundaries most major interactions happen on the boundary of the plates They are constant motion Some plates are purely oceanic and others like South and North American plates have both land and oceanic There are 3 types of boundaries Divergence 2 plates move apart Usually results in new sea floor Convergent Move toward each other Usually results in collision or subduction of oceanic plates Transform plates grind past each other and does not affect lithosphere Changing boundaries plate boundaries are created from changes of force going towards the lithosphere Some plates get bigger because of divergent boundaries while some get smaller because of subduction or collisions These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Minerals Building Blocks of Rocks Common metals like copper and iron and precious metals like silver and gold occur as mineral ores Other everyday items we use Talc bath powder cosmetics Halite salt Graphite pencil lead Needs the following five characters to be a mineral 1 2 3 4 5 Naturally occurring Inorganic Solid Atom order specific Definite chemical composition Definition of rock A solid aggregate or mass of minerals Elements are basic building blocks of minerals 92 are naturally occurring Atoms smallest particles of matter Atomic Structure central region is the nucleus what has positive protons and neutral neutrons while negative electrons orbit it o Electrons move in an unpredicted path and forms a cloud Particles Atoms Minerals Rocks Composition of Minerals Chemical Bonding two or more elements combine to make a compound and are held together through chemical bonding Ionic Bonding transferring or electrons in order to achieve balance Covalent Bonding sharing electrons and are now stuck together Metallic Bonding Electrons are free to move around other atoms and is usually weaker than ionic and covalent bonds Structure of Minerals Minerals have an orderly array of atoms in a specific crystalline or geometric structure Polymorphs Minerals that have the same chemical composition but different structures such as diamonds and graphite Phase Change transformation from one polymorph into another Physical Properties Crystal Form o Shows internal arrangement of atoms that can be seen by the naked eye o Best grows in open spaces o Growth can be interrupted because of space and loss of heat Luster o How it looks in reflected light o It can be metallic shiny or dull like Talc or Quartz and it can be nonmetallic silky pearly soapy like Pyrite or Galena o Some show a submetallic luster Color o Unreliable to identify a mineral but it is a property o It can be a huge variable for a mineral because some can have impurities in the chemistry o Exotic colors produce gemstones Streak o Color of mineral in powdered form o Streak will be the same NO MATTER WHAT The color will not vary even if the color of the mineral is different o Metallic streaks are darker than nonmetallic streaks Hardness o Mineral resisting scratching or bruising o All minerals are composed to Mohs scale of hardness numbers 1 10 o For example If you scratch a mineral with your nail it is sofer than 2 5 Cleavage o Break on planes with weaker bonds o Breaks into shiny flat surfaces o Described by geometric shapes like number of planes and angle between the planes Fracture o When there is no cleavage but when broken has a dent instead called a conchoidal Specific Gravity o Found by dividing weight g and volume cm3 o Some are more dense and heavier than they appear Other Minor Properties o Magnetism o Reaction to Acids o o o o Smell Feel Taste Double Refraction