What Did I See at
Vasquez Rock?
Follow-up to our class trip to
Vasquez Rock
Desert Varnish
• Surface covered by
black deposits called
rock varnish
• Layer consist of thin
layer of bacteria, clay
minerals, and
manganese and iron
oxides
• The Mn oxide (MnO2)
makes black color
Stop #1-2
Solution Holes (Tafoni)
• Result of local wind
turbulence on wet rocks
• Wind evaporates water
(H2O)and causes the
growth of tiny salt crystals
at and below the surface
of the rock causing
pressure on the sand
grains
• Sand grains loosen and
form small cavities, which
continue to weather from
the wind causing the
cavities to grow
Stop #1-2
Do Plants Grow on Rocks?
Stop #1-4 Juniper Bush
• Bacteria and lichens first break away rock and
minerals (clay and sand)
• Dead bacteria provide organic matter providing
nutrients for plants to grow
Bedding Planes
Stop #1-5
• Criteria to distinguish
one bed from another:
–
–
–
–
Grain size
Color
Resistance to weathering
Grain composition
• Reddish color–iron oxide
• Occurs when sediments
are deposited on land
and are exposed to the
atmosphere
Displacement
Stop #1-6
• Sedimentary strata
form continuous
layers
• Cracks where there
been displacement
are called faults
• Offsets usually
produced by
earthquakes
• Red color is not Iron
Oxide instead red
paint
Chemistry in Action