#doline

The first time I saw S12E11 “Surface Tension” I couldn’t stop thinking about my real situation.

LUKE (my boyfriend):

“It's what I thought. Heavy concentration of silky clay mixed with gravel and rock. And it's not a natural soil composite for the area, but it was present at all 3 disposal sites.”

EMILY (a poor person who got in the way):

“Which tells us what?”

LUKE:

“Well, it's used to repair sinkholes. And all of the victims, they were placed just inside the transition area.”

ROSSI (me):

“You hear that, Reid?”

SPENCER (his genial friend):

“I did, and, you know, it fits with our profile about the unsub making a statement about environmental ruin. You know, sinkholes have been on the rise, actually, worldwide, due to urbanization, drilling, fracking.”

EMILY: 

“Garcia?” 

PENELOPE (the other part of me):

“She's here. Feed the beast.”

EMILY:

“What can you tell us about sinkholes in Florida?” 

PENELOPE:

“I can tell you that... Jinkies. Tread lightly, there are a gazillion of them. Over 500 in the Tampa Bay area alone since records started being kept in 1974. Why are you asking?” 

EMILY:

“We think our unsub is taking his victims to current or former sinkholes.”

ROSSI:

“We're trying to anticipate which one he might pay a visit to next.”

SPENCER:

“Guys, are they cover-subsidence or cover-collapse sinkholes?” 

LUKE:

“Given their shallow layer of repair, I'd say they're cover-subsidence.”

ROSSI:

“I'd chime in with an opinion as well if I knew what the hell you two were talking about.”

Rossi in the last sentence is me everytime I find me between geologists. -.-

Red and Blue lake

The sinkholes of Crveno Jezero (Red Lake) and Modro Jezoro (Blue Lake) are located only a few hundred meters apart in the Dalmatian province of eastern Croatia, near the border with Bosnia-Herzegovina. The sinkholes formed by underground rivers penetrating the Cretaceous limestone above and the dolomite below. The area contains around 18 small and big water filled depressions.

Crveno Jezero is nearly circular and 528m deep with a diameter of 450-500m making it the third deepest sinkhole in the world. It is filled with dark blue water to a depth of 290m and contains 16 million cubic m of water. The depth of the lake was confirmed by an expedition of speleodivers in 1998. At the bottom of the lake a cave canal is orientated to the southwest. However, this cave canal has not been mapped yet. Actually quite a number of caves are present near the water level of the lake.

Locally, Crveno Jezero is known as Red Lake which is not due to the red color of the water (it is actually quite blue) but to the red cliffs that surround the sinkhole. The redness of the cliffs is caused by the presence of iron oxides, an element of the common soiltype known as Terra Rossa which is found throughout the Mediterranean. The cliff walls are almost vertical except for one side which collapsed during an earthquake in 1942. Because of its depth and the dangers of collapsing cliff walls the lake is not accessible (not mentioning that it is a daredevil climb down to even get there although you could also base jump). Crveno Jezero is also home to the endangered species of fish called Delminichthys adspersus. This small fish (12cm) are solely found in the Dinaric Alps of Croatia, they require extremely clear water which is found in this region commonly. Sometimes the fish are found in springs surrounding the sinkhole which indicates that underground the sinkhole is connected to other water bodies.

Only a few hundred meters next to Red Lake is Modro Jezero known as Blue lake due to its intense blue-green color. Unlike the almost perfectly circular Red Lake Blue Lake is oblong. The lake is up to 90m deep but is known to disappear completely at the end of summer. Overall the Blue lake sinkhole reaches a depth of 290m from top to bottom. Here, the 1942 earthquake also caused a large landfall which reduced the depth of the lake. Unlike Red Lake Blue Lake is a popular place for swimming since it is not as deep and easily accessible. The appearance of a boulder in the lake, named Jakićin after a boy who drowned here in 1834 usually marks the beginning of the swimming season. When the lake dries up in the summer local soccer matches are played in the middle. The southern nearly vertical rim is often used for cliff jumping (into the water ). As with Blue lake the sinkhole is surrounded by other small caves. The 9th century fortress of Imotski towers above the high cliffs. Hiking trails around the lake were build in 1907 under reign of the Habsburg emperor Franz-Josef.

--BO

Image: Courtesy of www.travelcroatia.com. Red Lake seen from above.

References:

http://www.wondermondo.com/Countries/E/Croatia/SplitDalmatia/CrvenoJezero.htm Here you can see a cross section of the cave as compared to a large airplane.

http://www.cavernas.org.br/anais26cbe/26CBE_555-559.pdf