6 Glaciers: Then and NowStudents compare photographs of glaciers to observe how Alaskan glaciers have changed over the last century.
7 About Glaciers…Continental glaciers (ice sheets) cover large areas of land.Alpine glaciers (valley glaciers) fill high mountain valleys.How glaciers change:Glacial advance: Glaciers become larger when more snow falls than melts.Glacial retreat: Glaciers become smaller when more snow melts than falls.
8 Glaciers MOVE! Glacial ice flows slowly downhill in two ways: Internal deformation: plastic movement within the ice (think: slow-flowing honey.)Basal slip: the entire glacier slides on its base (think: slipping on a banana peel.)What factors affect how fast a glacier moves?
9 Model a Moving GlacierThis activity allows students to experiment and discover how three variables affect glacier flow:- valley slope- ice temperature- basal conditions (ground surface)
10 Models of glaciers using “flubber” Flubber glacierFlubber is a polymer that has the properties of both a liquid and a solid. The molecules in the flubber are loosely arranged and can slide past each other.Actual glacierfood coloring (optional)½ cup warm water1 cup white glue2 tsp. of Borax¾ cup warm waterMix #2Mix #1
11 What factors affect how fast a glacier moves? Test it!What factors affect how fast a glacier moves?Valley slope:ShallowMediumSteepBasal conditions:Rough – sandpaperNormal – plain PVC pipeLubricated – Foil and oilPick a variable.Make a hypothesis.(e.g. the steeper the slope, the faster the flow.)Flubber in action
12 Ice Over Water: Sea IceSea ice is frozen seawater. It can be several meters thick.During summer much (but not all) of the sea ice melts.During winter more sea ice forms again.
13 Graphing Sea Ice Extent Students graph sea ice extent (area) in the Arctic and Antarctic over a three-year period to learn about seasonal variations
14 Graphing Sea Ice Extent Then, students graph sea ice extent over a 25-year period to learn about longer-term trends.
15 Earth as a system: It’s all connected! “I don’t live anywhere near glaciers or sea ice. Why should I care if the ice melts?”Earth as a system: It’s all connected!
16 Melting sea ice means less energy is reflected causing more global warming. Credit: NSIDCMelting glaciers means more water in the oceans causing sea level rise.Data from 23 tide gauge stations on tectonically stable continental margins (R.A. Rohde/Global Warming Art Project)
17 Looking into Surface Albedo This activity demonstrates how the color of materials that cover the Earth affects the amounts of solar energy absorbed.Albedo is the amount of energy reflected by a surfaceDark colors – low albedoLight colors – high albedo