POROSITY AND PERMEABILITY
Review and Quiz
Water drains
downward through
the unsaturated
zone due to gravity.
The water table is
located at the top of
the saturated zone.
The saturated zone
is the area filled with
groundwater.
Why?
POROSITY – the percentage of open pore
space between rock particles (sediment)
Big spaces,
not a lot of
them
Example: conglomerate
Little spaces,
but lots of
them
Example: sandstone
Recalling the recent Porosity and
Permeability lab, make your
hypothesis.
How do you predict the
relationship between porosity and
permeability?
IOW, does porosity affect
permeability?____________
1st trial:
look at
red
yellow
green
only
Demo #1
Which size
held the
most water?
Demo #1
Porosity - Amount of open space between sediments
Big spaces, not
a lot of them
Little spaces
but lots of them
LESS surface
area
GREATER
surface area
IMPORTANT TO REMEMBER
The size of the rock particle DOES NOT change the porosity!
Porosity - The amount of open space in between rock particles.
Porosity is determined by
POROSITY
1. Shape - Well rounded particles have greater porosity than
angular particles.
ROUND
ROUNDNESS
ANGULAR
POROSITY
2. PACKING- The more closely packed the particles
are, the lower the porosity.
PACKING
UNPACKED
PACKED
POROSITY
3. SORTING- If all particles are the same size, they are sorted.
- If the particles are different sizes, they are
unsorted (poorly sorted)
- The more sorted the particles, the higher the porosity
SORTING
Particle Size alone
does NOT affect porosity!!!!!
(Shape, Packing, Sorting does)
The porosity is the same for sorted particles, but not for unsorted particles.
Look at the mixed
sediment tube!
Why?
water to pass through it.
(tap on the curved red arrow to see the graph!)
Look at the arrows below!!!
PERMEABILITY
 PERMEABILITY - the ability of rock material to allow
PARTICLE
SIZE
Which one will drain the fastest?
Make your hypothesis
Permeability!
Which one is
the fastest?
Which one drains the fastest?
Demo #3 Hypothesis Page
Simulation #3 Permeability of Materials
(Click on Simulation #3 above to see the demo)
Demo #4 Rates of Deposition
Click play
below
 CAPILLARITY – the process of water adhering to rock
particles (cohesion) in small spaces, resulting in an
UPWARD movement of the water through rock
sediment.
The height water will rise in a small cylinder (capillary tube) so it
is dependent on the diameter of the tube.
The effect of capillarity in soil pores can be seen between the
glass beads above. Water was added to the beads when they
were in contact, then the beads were separated. The water is
adhering (sticking) to the beads, but cohesion keeps a strand of
water between the beads. This is how water moves up a capillarity
tube by water molecules attaching to each other.
A quick review
Remember!
Porosity does not depend on grain size
HOWEVER…
As particle size
permeability
As particle size
capillarity
POORLY-SORTED PARTICLES: unsorted, mixed
sizes (not in layers)
WELL-SORTED PARTICLES: same size (in layers)
USING WHAT YOU LEARNED
FROM VIEWING THE ABOVE
SLIDES
ANSWER THE FOLLOWING 10 QUESTION QUIZ ON
THE INDEX CARD PROVIDED BY YOUR TEACHER.
1. Put your name on the top of the lined
side of the index card.
2. Number each question.
3. Skip a line in between each question.
4. Turn in Quiz by next class!
The diagrams below represent three containers, A, B, and C, which were filled
with equal volumes of uniformly sorted plastic beads. Water was poured into
each container to determine porosity and infiltration time.
1. Which data table best represents the porosity and
infiltration time of the beads in containers A, B, C?
A
B
D
2. Soil composed of which particle size usually
has the greatest capillarity?
A) fine sand
C) silt
B) pebbles
D) coarse sand
3. When rainfall occurs, the rainwater will
most likely become surface runoff if the
land surface is
A) impermeable
C) sandy
B) nearly flat
D) covered with grass
A student performed a laboratory activity in which water
was poured slowly into four cups containing equal volumes
of loosely packed sediment samples, as shown in the
diagram below. All particles were spherical in shape and
uniform in size within the container. After the water
level reached the surface of each sample, the student
determined the amount of water that had been added.
4. The results of the activity should have indicated that
approximately equal amounts of water were added to the cups of
A) silt and pebbles, only
B) sand, pebbles, and the mixture, only
C) pebbles and the mixture, only
5. Which graph shows the effect of soil
permeability on the amount of runoff in an area?
6. The diagrams below represent four permeable
sediment samples. The sediments are composed of
the same material, but differ in particle size
and sorting. Which sediment sample will most
likely have the fastest groundwater infiltration
rate? And why?
7. What size rock particle can be transported by a
stream moving at a velocity of 100 cm/s?
A) fine sand
B) pebbles
C) silt
D) coarse sand
8. The climate of Phoenix, NY, located in the
northeastern part of the continent, ranges from warm
and wet in the summer months to cold and snowy in the
winter. What type of weathering do we experience
according to the below climate graph?
A) yellow--strong chemical
B) green--moderate chemical
with frost action
C) blue--slight physical
D) purple—strong physical
9. If the amount of precipitation for an area
was 125 cm/yr. and the average yearly
temperature was 5oC, what type of weathering
would be experienced in this region?
A) moderate chemical
B) strong chemical
C) Very slight
D) Moderate chemical
with frost action
10. FOLLOW THE BELOW INSTRUCTIONS EXACTLY.
If your last name begins with letter A – M, answer the following
question:
QUESTION: If the porosity of a material decreases, how will the
permeability be affected? (increases, decreases, or stay the same)
If your last name begins with the letter N – Z, answer this question:
QUESTION: Which of the following materials would have greater
permeability?
A) a gravel pit
B) a sandy beach
C) a muddy field
D) an asphalt parking lot
10 questions
10 pts. each