Transcript Weathering
Reminders: • Prepared • In Seat, with materials ready to go when bell rings. • Scrap Paper ALWAYS available & pen/pencils check bucket or ask • Polite • If you can’t say something nice, keep it shut. • Don’t mess with other’s belongings. • Clean up after yourself. • Prompt • Turn in work on time, • When absent get work (1 day/1 day absent) & turn in, if miss exam, by next day otw “0”. Make arrangements. • Test grades are POSTED, I do NOT pass back exams. • 3 days for correction & retake* after grade posted. * You must have ALL work turned in before a retake will be given. Reminders: • Fire Drill • Out to practice field • Lock down • Lights out, up against wall, quiet, phones off • If possible, • I will ask help to block doorways with tables, etc… QUIETLY • Pass out books, to throw as distractions (volunteer) • Severe Weather • Stay in classroom, tables against walls, under tables • Lock out • Classes continue as normal, although remain in bldg. Reminders: • Duty • Monday am – Library • Monday pm – Parking lot • Tutoring/Test Make-up • M-F @ lunch by APPT., • Please get pass & check with me for availability • T-F after school • Please check with me for availability • T & W often meetings Reminders: • Have you signed up for Remind? • If not, do so! I send out reminders, worksheet copies, you just never know… HINT! HINT! HINT! • Check Class Web Page for ppts., assignments & notes • My email: [email protected] Weathering, Erosion & Deposition ESS 2015-16 Weathering • The breaking up of rock into smaller pieces Mechanical (physical) • When rocks are broken apart by a physical force. Abrasion – • Moving water or wind carries sand or other particles that wear away rock surfaces. Ice Wedging • Freezing water in cracks of rocks expands causing rock to be further fractured. – Organic activity • Plants, animals or people can loosen soil & rocky material. Organic activity • Plants – “root wedging” or “root action” Gravitational Impact (Mass Wasting)) •Occurs due to gravity pulling sediment downward and breaking it into smaller pieces. Gravitational Impact • Creep • Rock slide • Mudflow • Earth flow Glaciers • Carry boulders on underside, these boulders grind away at surface underneath Chemical Weathering • Chemical weathering breaks down bonds holding the rocks together, thus they fall apart, forming smaller and smaller pieces. Chemical Weathering • More common where there is a lot of water. • Water is important to many of the chemical reactions that can take place. • More common where temperatures are warmer. Chemical Weathering Most common types of chemical weathering • Oxidation • Hydrolysis • Dissolution • Plant acid • Hydration Oxidation • Rocks containing metals are combined with oxygen to form “rusts”. • The areas in these rocks that are oxidized are weaker & thus more susceptible to physical weathering. Hydrolysis • A reaction with water in which a molecule is cleaved into two parts by the addition of a molecule of water • Affects silicate and carbonate minerals. • Pure water ionizes & reacts with silicate minerals. Hydrolysis Don’t need to write this Example Mg2SiO4 + 4H+ + 4OH- ⇌ 2Mg2+ + 4OH- + H4SiO4 Olivine (forsterite) + 4 ionized H2O molecules ⇌ ions in solution + silicic acid in solution Dissolution • Slightly acidic water dissolves rock. • Carbonic acid • Sulfuric Acid Dissolution Marble & Limestone When carbonic acid is combined with a mineral like calcite (CaCO3), calcium and bicarbonate ions are released and carried off by groundwater. CaCO3 + H2CO3 Ca+2 + 2 HCO-3 Don’t need to write this Dissolution • Sulfurous gas (volcanoes & factories) can dissolve in water to form sulfuric acid. Acid Rain • SO2 + H2O H2SO4 Plant Acid • Mosses and lichens produce weak acids that dissolve the minerals that hold rocks together. Hydration • H+ and OH- ions attach to the atoms & molecules of a mineral. • Increases volume within rock, creates stress & breaks rock down Rates of weathering Factors : • Amount of surface area exposed to chemical weathering • Type of mineral • Climate • Especially warm & wet Don’t need to draw this, but understand reasoning