Glaciers

Glaciers

1. Snow transforms into Ice

   • Air is squeezed out through compaction
     • Increases pressure which generates heat
       • deforms snow into crystalline structure

2. Although 18th C glaciers were known to exist never thought they had existed in Scotland

   • Hutton never accepted glaciers had existed in Scotland
     • Stuck in Alps, all they'd ever been
   • Murchison and Lyell waivered towards end of careers

3. Erratics

   • Rock which does not belong to surrounding rock. Stranded. Can be HUGE
   • People believed arrived via Ice Berg during Noah's Flood
     • To 18th C mind this easier to accept
   • Moved due to Glaciers
     • Louis Agassiz
       • Swiss geologist
       • 1830's
       • At least One Ice Age
     • Glaciers moved erratics and caused Striations on underside of rock
       • Ice bergs could not cause this
         • Ice berg would have just melted

4. Glacial and Interglacial periods

   • Solar and volcanic activity insignificant
   • Wider variability can be seen but prob amplified by interglacial period now
   • Croll - Milankovitch hypothesis
     • 3 orbital cycles work different rates
       • When combined = major climatic changes
     • Tilt / Obliquity
       • 41000 yr cycle
       • S. Hemis tilted toward Sun presently
         • S. warmer Summer than N.
         • 23.5 degree angle
       • angle between 21.5 - 24.5
         • varies over long time periods
       • as tilt changes differential heat between N & S over long time periods
     • Elliptisity
       • nearly circular to v. elliptical
       • 100,000 yr cycle
       • orbit of Earth round Sun
         • varies due to gravitational pull from other planets in system
       • furthest in July closest in Jan
     • Wobble / Precession
       • 23,000 yr cycle
       • over time closer or further from sun
         • affects solar radiation recieved

5. All work <1950 done continenets

   • 1950 recognise 4 Ice Ages
     • Ice Ages removes evidence of previous Ice Ages
     • drilled oceans
   • Foramnifera
     • near ocean surface
     • skeletons of CaCO3
       • traps O2
     • when dead fall to bottom of ocean forming layers
       • perfect stratigraphic order