1 / 19

GEOL 208 Lecture 3

CON U

toddbee
Download Presentation

GEOL 208 Lecture 3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 0 Geology 208: The Earth, Moon and Planets Today a. Geology of the Earth: Skinner (2005 ed.), chap 1: 17-20, 23-28; chap. 2: 33-61 b. Climate change: Strahler (Canadian ed.) chap. 5: 122-130 c.Glacial processes & landforms: Strahler (Canadian ed.), chap.20: 593-621 Next class (May the 21st) Quiz # 1 (18:30): please be in your seats by 18:20 “The Origin of the Solar System”

  2. Weathering • process which acts at/near the Earth’s surface to decompose & break down rocks/rock-forming minerals • 3 types physical (mechanical) chemical (c) biological  transition between parent material & soil - occurs in place (in situ)... no transport or movement

  3. Physical Weathering primary effect gradual reduction in strength of bedrock, large rock fragments & boulders breaks them into smaller pieces of rock / constituent parts (disintegration) - sedimentary rocks individual grains defined by derived materials i.e. chalk (CaCO3, calcite/fossiliferous limestone) chalk powder

  4. Physical Weathering • igneous & metamorphic rocks individual crystals • i.e. potassium feldspar (igneous) quartz 3/6/2014 4

  5. Weathering (physical) 1.frost action = (ice wedging, ice cracking) (a) water freezes in rock fractures/joints (produced by physical weathering) & in sed. bedding planes (b) 9% vol. increase generates extremely high pressure        (c) optimum temp. for max. water pressure = -50C to -150C

  6. Weathering (physical) http://www.gly.fsu.edu/~salters/GLY1000/10Weathering_Erosion/Slide27.jpg Frost action (south of Inuvik, NWT, along Dempster Highway)

  7. 2.crystal growth (a) precipitation of sulfates, chlorides & carbonates... [i.e. evaporated sea spray; saline solutions] ...into cracks and joints  (b) leaves crystal residue; when heat…expand…increase in pressure ----------------- 3.plant roots,stem pressure (a) infiltration of cracks by roots & stems (within/between grains) (b) stems/growth tips of plant rootlets... ...may be strong enough to... ...loosen mineral grains & pry them apart http://upload.wikimedia.org/wikipedia/commons/f/fc/YehliuTaiwan-HoneycombWeathering.jpg http://cse.cosm.sc.edu/erth_sci/Soil/fig6_10.jpg

  8. Weathering (chemical) Decomposition of rocks by surface/near-surface processes (affects changes in original chemical/mineral (de)composition) chemical weathering (like physical weathering)  the strength and permeability of the rock decreases resistance to fluid and gravitational stresses (a) precursor to erosion (b) in situ,like mechanical weathering (c) temperature sensitive - may operate in conjunction with mechanical weathering -

  9. Weathering (chemical) i.e. oxidation  Fe2+(iron) combined with oxygen + water = oxides such as limonite

  10. Erosion Removal of solids from (in situ) weathering sites by wind, water, ice or gravity, etc.

  11. granite, minerals are quartz & feldspar Rocks feldspar (potash) potassium alumino silicate • Naturally occurring solid aggregate of minerals • can be categorised by mineral content & • formation processes, of which there are - • 3 Types • 1. Igneous; 2. Sedimentary; 3. Metamorphic

  12. Minerals naturally occurring inorganic substance usually possesses a characteristic sometimes crystalline atomic structure i.e. quartz

  13. Igneous • formed by crystallisation & solidification of magma •  • Types • by cooling rates • 1. intrusive (cooled slowly in crust, large crystals, i.e. granite, gabbro) • 2. extrusive (cooled rapidly on the surface, fine grains, i.e. basalt) • variation also due • (b) original composition of magma • (c) reheating and recomposition of surrounding rocks 13

  14. http://www.geo.umn.edu/mgs/virt_egg/granite.jpg Igneous (intrusive) http://web.umr.edu/~rogersda/grand_canyon_research/ Granite%20Gorge%20at%20Phantom.jpg granite (intrusive, slow cooling, large crystals) Granite Gorge (Grand Canyon) 14

  15. Igneous (extrusive) basalt (extrusive, fast cooling, small crystals) gabbro (intrusive, slow cooling, large crystals) 15

  16. Sedimentary …formed by… weathering(in situ) or erosion(transported) rock/mineral material (rock fragments & mineral grains) (a) deposition & consolidation of material in horizontal (beds or strata)layers (b) compaction / cementation by overburden pressure  process called “lithification” Sandstone Canyon, Utah 3/6/2014 3/6/2014 16 16 16

  17. Sedimentary • a) clastic(i.e. rock fragmentsediments • weathered • sand (quartz):large grains; clay particles: fine grains • (b)chemical sediments • precipitated i.e. from solution in water • calcium carbonate, • (derived from shells of marine organisms) clays calcium carbonate 17

  18. Metamorphic shale (fine-grained sedimentary rock) slate (metamorphic rock) rock alteration by intense heat and/or pressure (i.e. induced by tectonic movement) - re-crystallisation, but no melt (igneous) phase - changes mineral assemblage / texture (but memory of previous life retained) 18

  19. Rock cycle Igneous - from molten rock Sedimentary - weathered, eroded & compressed… - …from rocks & biogenic materials Metamorphic - rocks changed by heat &/or pressure, but not molten Cycle constantly transformation, one type to another 3/6/2014 19 19

More Related