In 2009 a man fell into a sinkhole 20 meters
deep near the Dead Sea in Israel during a trip in that area.
A sinkhole is a hole in the ground caused by
the collapse of the ground surface layer as a result of certain natural
It is known that in the Dead Sea area, salt layers buried underneath the ground surface are covered by salty groundwater that is in a saturated solution state. It is also known that the sinkholes' phenomenon is related to the fact that every year the Dead Sea water level declines. Water level decline causes the salt layers to be flooded by fresh groundwater.
The question is closely related to the picture, the video
and the geographic location.
Solving the question involves deep understanding of the topic
and thorough thinking. The picture and the video add much info and help answering
the question. A picture is worth a thousand words. For example, we can see that
the fresh water appears above the salt layer, so we can imagine how it
dissolves the salt.
You’ve used an actual occurrence from local news.
Minor items for improvement:
Try keeping the answer
variants of a similar length.
Try keeping the map points as
close to your location as possible, e.g. sinkholes in Mexico.
I would add a more detailed
sketch and a photo of a sinkhole to the question, like these: sketch,
Good Job: Question and Topic
First and foremost, I want to say that the question is
great and is relevant both to student's from abroad and especially to student's
here in Israel where the phenomena has become widespread in recent years.
Although, I would like to raise a few points to think
A wise and educated student
who is aware of the fact that the dead sea is located in a desert zone with no replenishing
water sources, would find it hard to understand the sudden source of fresh
water that dissolve the salt layer in the ground creating the sinkholes.
The diagrams presented to
the student as part of the material the
question is built upon, does not supply the dimension of time in which
the fresh water appears. A short explanation about floods phenomena in the area
is needed to explain to the student why and how fresh water gets in contact
with the salty ground. In addition, there needs to be an explanation about the retreatment
of the sea and the exposure of the salty ground to the sudden flush of the
fresh water coming from the floods. This ultimately break's the natural circle
that one's was present in the area. The dissolving of the salt by the fresh
water coming from the floods is fairly quick due to the fact they are not
saturated with salt almost at all. The sea however cannot replenish the salt in
the rock anymore because it is no longer in contact with it, thus endorsing the
formation of sinkholes in the area.
A very interesting question and is related to
our daily lives, not only scientific knowledge but also everyday life and in
addition to that this question is relevant for students in Israel and to
students from the rest of the world ,that the above phenomenon is very common
phenomenon and could occur in our lives every
• Try to keep the points close to your
location on map as far as possible sinkhole, for example, sinkholes in Mexico.
• I think that a student does not have to
think much in order to answer, immediately after he read the paragraph, you
showed the relationship between the water level and the phenomenon of formation
sinkholes in the paragraph and explanation of the chemical side in the animation,
so I would use the image alone without an explanation of each phase, and begin
the paragraph with an accident that occurred in a particular place were roads
closed due to a sinkhole, and so the simulation will be enough.
• I would further add a video of sinkholes
occurrence because some students do not even know what a sinkhole is and how it
I would like
to thank all who commented. It is very nice to get such supporting comments. Thank you all also for
the suggestions. However, we preferred to keep the question simple and not too
long, so we added information through the points on the map, such as a sample
of a sinkhole, though in Mexico. It would have been better in the Dead Sea, we
It was important for us
that the students will make the right connection between the scientific knowledge
of saturated and un-saturated solutions and what is happening under the ground
of the Dead Sea. This connection is the heart of the question. I can accept
Olfat suggestion to take out the chemical explanation in the animation to make
the question more difficult but the animation is not the answer so the student still
has to figure out the right connection that explain the sinkhole formation.
I would like to add
something to Ohad about the fresh groundwater. We did not explain their
presence since this is not essential information to the question and did not want to prolong the question unnecessarily. Actually we assumed they are originated
from rains. Although the Dead Sea area is a relatively dry area, it gets rain, and heavy rain
Because there is another point about the sinkholes in dead sea, I decided to add another point that explains the difference between saltwater and freshwater .you can see this point in the map (wael's home).