Snow and Ice as Sediment and Rock?

1. Snow and Ice as Sediment and Rock? Snowflakes as Mineral Crystals!

2. Analogs for rock-forming processes Ideas from William D. Romey’s “Winter Ice and Snow as Models of Igneous Rock Formation” (1983)

3. . . . and glacial ice a an analog for metamorphic rock . . .

4. How does water differ from silica? How do melts (magmas) of water and silica differ?

5. Flow structures: frazil ice and lava bars pressure ridges and tumuli dikes and sills

6. icicles and lavacicles!

7. From snowflake to hoar and firn . . . and fluid inclusions in sea ice

8. corn snow and gruss?

9. Melting of the ice covering rivers and lakes can serve as a useful analog in helping to understand what goes on deep below the earth’s surface where silicate magmas are generated.

10. The break-up of ice on rivers and lakes also provides analogs of plate-tectoncis mechanisms: fracturing, rifting, subducting.

11. Working in pairs, make a • concept map of a section of • Snow and Ice as Models of • Igneous Rock Formationby W. Romey. • Simplest directions: • Read the section • Decide upon a focus question • List key concepts • Arrange concepts (by association and hierarchy) • Link the nodes • Label the links Revise the map as needed after any step!

12. Do not worry about all of the technical terms in the Romey “Snow and Ice as Models of Igneous Rock Formation.” Look for concepts that organize the information. Remember that the “big idea” is that analogy plays an important role in geologic reasoning. Eutectic point: the common melting and freezing temperature of a homogeneous mix of minerals at a particular pressure and in just the right proportion to each other. For example: the freezing temperature of salt water. Anatexis: the partial melting of rock, typically at temperatures well above 600o C and often leading to the formation of metamorphic rock.