Abarkuh Sinkholes

The Sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. Most are caused by karst processes—for example, the chemical dissolution of carbonate rocks or suffusion processes. Sinkholes vary in size from 1 to 600 m both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide.(wikipedia)

Abarkuh County in south-west of Yazd province in center of IRAN have faced with some sinkhole occurrences in recent years which have caused significant damages to agriculture lands and other infrastructures of villages in this area.

From 2000 to 2005 more than 30 sinkholes had happened near Faizabad village. According the geological map of this area, sinkholes have formed on quaternary layers with maximum 13.5 meters and minimum 0.5 meters deep.

Photo by: Siamak Mohammadi Sivandi

 

Keywords: Abarkuh , Geology , Geotourism , Iran , Quaternary , Sediment , sinkhole , underground water , zamingasht

Lahar

lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley.

Lahars are extremely destructive: they can flow tens of meters per second (22 mph or more), be 140 meters (460 ft) deep, and destroy any structures in their path.

A lahar is a volcanic mudflow or debris flow. Lahars have the consistency, viscosity and approximate density of wet concrete: fluid when moving, solid at rest. Lahars can be huge.

A lahar of sufficient size and intensity can erase virtually any structure in its path, and is capable of carving its own pathway, making the prediction of its course difficult. Conversely, a lahar quickly loses force when it leaves the channel of its flow: even frail huts may remain standing, while at the same time being buried to the roof line in mud. A lahar’s viscosity decreases with time, and can be further thinned by rain, but it nevertheless solidifies quickly when coming to a stop.

Lahars vary in size and speed. Small lahars less than a few meters wide and several centimetres deep may flow a few meters per second. Large lahars hundreds of meters wide and tens of meters deep can flow several tens of meters per second (22 mph or more): much too fast for people to outrun. With the potential to flow at speeds up to 100 kilometers per hour (60 mph), and flow distances of more than 300 kilometers (190 mi), a lahar can cause catastrophic destruction in its path.

Lahars have several possible causes:

  • Snow and glaciers can be melted by lava or pyroclastic flows during an eruption.
  • Lava flows out of open vents and can mix with wet soil and mud on the slope of the volcano making a very viscous, high energy lahar. (The higher up the slope of the volcano the more gravitational potential energy the flow will have.)
  • A flood caused by a glacier, lake breakout, or heavy rainfall can release a lahar, also called glacier run or jökulhlaup
  • Water from a crater lake, combined with volcanic material in an eruption.
  • Heavy rainfall on unconsolidated pyroclastic deposits.
  • Volcanic landslides.

In particular, although lahars are typically associated with the effects of volcanic activity, lahars can occur even without any current volcanic activity, as long as the conditions are right to cause the collapse and movement of mud originating from existing volcanic ash deposits.

  • Snow and glaciers can melt during periods of mild weather
  • Earthquakes underneath or close to the volcano can shake material loose and cause it to collapse triggering a lahar avalanche.
  • Rainfall can cause the still-hanging slabs of solidified mud to come rushing down the slopes at a speed of more than 30 kilometers per hour (20 mph), causing devastating results.

Damavand volcano is the tallest volcano in Iran and Asia (5671m.). This volcano is currently a semi-active volcano. Smoke and steam come out from the volcano, but it has not erupted for years. Its last volcanic activity was 38,500 years ago (based on age determination by carbon 14). The mountain range is covered by frequent lava streams that have been flooded with peaks from the summit or sub-cones, as well as pyroclastic materials such as Pumice, Tuff and Lahar.

Lahar deposits accumulated around the city of Rudehen (near Tehran) are shown in the image. These deposits were flowing down the slopes of the Damavand volcano in ancient times. These deposits consist of fine grained deposits (ash) and large and small boulder(lava).

Keywords: Iran Geology , Iran Geotourism , Lahar , Rudehen , Tehran province , zamingasht

Reference: wikipedia

Bedding

In geology a bed is the smallest division of a geologic formation or stratigraphic rock series marked by well-defined divisional planes (bedding planes) separating it from layers above and below. A bed is the smallest lithostratigraphic unit, usually ranging in thickness from a centimetre to several metres and distinguishable from beds above and below it. Beds can be differentiated in various ways, including rock or mineral type and particle size. The term is generally applied to sedimentary strata, but may also be used for volcanic flows or ash layers.

In a quarry, a bedding is a term used for a structure occurring in granite and similar massive rocks that allows them to split in well-defined planes horizontally or parallel to the land surface.

Three kinds of beds are: parallel beds, cross beds, and graded beds.

In the Image, thin and arranged layers of tuff and shale of Karaj Formation can be seen. The layers are exiting and sloping due to the effect of the Tectonic forces. These layers were formed by the sedimentation of fine-grained sediment and volcanic ash in the Eocene (55 to 38 million years ago) on the seafloor at that time. The thickness of these deposits is now more than 3,300 meters. When the layers are regular and in fairly equal thicknesses, they are called “well-bedded”. This is well seen in the image.

Keywords: bed , bedding , Geology , Geotourism , Iran , Karaj formation , Zamingasht

reference: wikipedia

Mila Formation in Central Alborz

The Mila Formation is one of the Cambrian formations in Alborz.  The Mila Formation has 5 measurable members in type section (Mila Kuh, Damghan City). This formation overlies conformably the Early Cambrian Lalun Formation and underlies disconformably the Early Devonian red conglomerates. But on the Chalus road in Central Alborz, four members of this formation are visible and measurable.

The first member is a white base quartzite (BQ), which in the past was a member of the lower formation (Lalun), but according to detailed studies, the boundary of this unit with underlying sandstone layers is considered to be discontinuous.

The Second member consist of Dolomite with interbedded of yellow Shale and Marl. Third member is well bedded Limestone with a few shale. Forth member is course grained glauconitic limestone. Fifth member consist of Siltstone, Sandstone, Glauconitic limestone and Marl.

In the Image, Mila formation outcrops in Chaloos road, near Hasanakdar Village. Because of the tectonic forces, the rocky layers are cut, broken, and displaced by faults.

The lower boundary of this formation with the Lalun Formation is para unconformity and indicated with the white quartzite layers. The upper boundary of this formation in this area is determined by the Hassanakdar fault and the outcrop of lava in the Geirud Formation. All the thickness of the Mila Formation (without quartzite) in the Karaj valley is 395 meters (Lorenz, 1964). In this region without the quartzite member, only three members of the Mila Formation have been identified.

In the photo, the formations of Lalun (La), Mila (Mi), Ruteh (Ru), Jeyrud (Je), Elika (El) and quartzite member of the Mila Formation (BQ) are seen.

Keywords: Iran , Central Alborz , Geology , Geotourism , formation , Mila , ruteh , jeyrud , elika , chaloos road , limestone , sandstone , siltstone , dolomite , shale , marl , zamingasht

Alborz Mountain Range

Alborz (Persian: البرز‎‎), also spelled as Alburz, Elburz or Elborz, is a mountain range in northern Iran that stretches from the border of Azerbaijan along the western and entire southern coast of the Caspian Sea and finally runs northeast and merges into the Aladagh Mountains in the northern parts of Khorasan. This mountain range is divided into Western, Central, and Eastern Alborz Mountains. The Western Alborz Range (usually called the Talish Mountains) runs south-southeastward almost along the western coast of the Caspian Sea. The Central Alborz (the Alborz Mountains in the strictest sense) runs from west to east along the entire southern coast of the Caspian Sea, while the Eastern Alborz runs in a northeasterly direction towards the northern parts of the Khorasan region southeast of the Caspian Sea. Mount Damavand, the highest mountain in Iran, is located in the Central Alborz Mountains.

The Alborz mountain range forms a barrier between the south Caspian and the Iranian plateau. It is only 60–۱۳۰ km wide and consists of sedimentary series dating from Upper Devonian to Oligocene, prevalently Jurassic limestone over a granite core. Continental conditions regarding sedimentation are reflected by thick Devonian sandstones and by Jurassic shales containing coal seams. Marine conditions are reflected by Carboniferous and Permian strata that are composed mainly of limestones. In the Eastern Alborz Range, the far eastern section is formed by Mesozoic (chiefly Triassic and Jurassic) rocks, while the western part of the Eastern Alborz Range is made primarily of Paleozoic rocks. Precambrian rocks can be found chiefly south of the city of Gorgan situated in the southeast of the Caspian Sea and in much smaller portions in the central and western parts of the Central Alborz Range. The central part of the Central Alborz Range is formed mainly of the Triassic and Jurassic rocks, while the northwestern section of the range is made mainly of the Jurassic rocks. Very thick beds of the Tertiary (mostly of the Eocene) green volcanic tuffs and lavas are found mainly in the southwestern and south-central parts of the range. The far northwestern part of the Alborz that constitutes what is called the Western Alborz Range or the Talish Mountains is made mainly of the Upper Cretaceous volcano-sedimentary deposits with a strip of Paleozoic rocks and a band of Triassic and Jurassic rocks in the southern parts, both in a northwest-southeast direction. As the Tethys Sea was closed and the Arabian Plate collided with the Iranian Plate and was pushed against it, and with the clockwise movement of the Eurasian Plate towards the Iranian Plate and their final collision, the Iranian Plate was pressed from both sides. The collisions finally caused the folding of the Upper Paleozoic, Mesozoic, and Paleogene rocks, and the Cenozoic (chiefly the Eocene) volcanism to form the Alborz Mountains mainly in the Miocene. The Alpine orogeny began, therefore, with Eocene volcanism in southwestern and south-central parts of the Alborz and continued with the uplift and folding of the older sedimentary rocks in the northwestern, central and eastern parts of the range during the orogenic phases of importance that date from the Miocene and the Pliocene epochs.

In the photo above, the mountain overlooking the plain of Tehran (capital of Iran) can be seen. The mountains have formed the southern boundary of Alborz Mountain. The highest peak in this section, is Tochal (3962 meters). In the far right of the photo, Mount Damavand (5671 m), the highest peak in Iran is seen. This peak is the highest volcano in Asia.

In the southern part of Alborz in northern Tehran, pyroclastic rocks, shale and volcanic rocks are abundant. This stones are called green series or “Karaj formation”. More than 3,000 meters of sediments were deposited at the Eocene in this part of the Alborz, and the Karaj formation is created.

The Photo was taken by Amir Hossein Azizian, over “Milad Tower” in Tehran.

Keywords: Alborz Mountain , Elborz , Elburz , Eocene , Iran Geology , Iran Geotourism , Karaj formation , Milad tower , Mountain range , Orogeny , Pyroclastic ,Tehran , Tochal peak , Volcanism , zamingasht

Namakdan Salt Cave

Namakdan cave is among the most important geosites in the Qeshm Island Geopark (Hormozgan province, Iran). The salt dome (diapir) of Namakdan is a unique structure in the Island including several outstanding structural, mineralogical, erosional and sedimentary sceneries. In this Geosite the world record Namakdan Cave exists, the world longest salt cave, 6500 meters.

The Namakdan Salt Complex (Combrian) actually includes several smaller geosites. There are Salt flats, Playa, Salt springs, Amazing salt outcrops, Sink holes and many other structure and forms. This geosite has been registered in the National List of Natural Heritages (2010).

The main entrances of cave are N1, N2 and N3. N1 is open for general visits; visit to N2 needs arrangements with geopark management and should be done by geopark guide assistance. N3 is very delicate and also dangerous; it is possible to visit just for speleology professionals, geology specialist’s holded particular, written permission from the Qeshm Island Geopark management.

There is a spectacular polygonal form on the southern wall of salt dome in front of the sea. This structure created by salt surface fractures and step erosion in the beddings surface at the same time.

Geology of Salt Dome and Salt Cave

Namakdan Salt dome has an outcrop of 7 kilometer in diameter. This feature has covered the western plunge of Salakh Anticline. Namakdan Salt Dome has been formed from Hormoz Series deposits (preCambrian-Cambrian).

Because of its plasticity nature, it was always inclined to rise up to escape the pressure by upper rocks. Field evidences and seismic logs shows that Hormoz Series had a very slow movement and uplifting; so caused to thinness of the sedimentary formations and making slop in the basement.

Namakdan Salt Cave is located inside Namakdan Salt Dome resulting Karst process and salt dissolution and forming underground channels and galleries. Inside the cave there are different types of sedimentary forms and speleothems. Erosion forms are more than sedimentary forms because of the water high capacity of saturation.

Keywords: diapir , Geopark , Hormoz Series , Hormozgan province , Iran Geology , Iran Geotourism , Namakdan Cave , Namakdan dome , Qeshm Island , world longest salt cave , zamingasht

Asmari formation

The Oligocene–Miocene Asmari Formation of the Zagros Basin is a thick sequence of shallow water carbonate. Asmari formation is the youngest and most important reservoir rock of the zagros Basin in the south-west of Iran.

The Asmari formation has been divided into two members: one is the Sandstone Member of Ahwaz in the south-west of the Khuzestan area and the other one is the Evaporate Member of Kalhor in the Lorestan Province. This formation is divided into three units: the lower Asmari with an Oligocene age, the Middle Asmari with an Aquitanian age, and Upper Asmari with a Burdigalian age. However, these divisions do not exist everywhere.

Also, in some parts of Iran, the lower boundary of Asmari formation is in contact with the Pabdeh Shale formation which is of Paleocene-Oligocene age, but in central Lorestan this formation is overlying the Late Eocene Shahbazan formation and in internal Fars it show a paraconformable contact with the Jahrum formation (Eocene).

The Asmari formation is covered by anhydrites of the Gachsaran formation which is of Early Miocene age, and in internal Fars the upper boundary of Asmari formation is in contact with the Early Miocene Razak formation.

The photo shows the Asmari limestone formation (As) and Gachsaran formation (Gs) Along the shore of Karun 4 Lake Dam near Lordegan city in Chahar mahal va bakhtiyari Province.

Keywords: Asmari formation , Bakhtiyari formation , Gachsaran formation , Geotourism , Iran , Iran Geology , Iran Geotourism , Pabdeh formation , Zagros Mountain , zamingasht

Emam hasan member

Gurpi formation is one of the formation in the Folded Zagros. This formation with bluish-green color consist of alternation of marl and grey shale with intercalations of thin bedded limestone.

This formation also has two limestone members so called “Emam Hasan” and “Seymareh”.

“Emam Hasan limestone member” consist of fine grained limestone, with thick bedded and grey in color with intercalations of marl. This member is feature forming than the other layers of Gurpi formation.

The age of Gurpi formation is Upper Cretaceous (Campanian-Maastrichtian (84 to 66 million years ago)).

The photo shows Emam Hasan limestone member in Anjir anticline in the south of Ilam.

Keywords: Cretaceous , Emam Hasan member , Gurpi formation , Ilam ,  Iran Geology , Iran Geotourism , Zagros Mountain , Zamin gasht

Qezel ozan river

Qezel ozan river is one of the longest rivers of Iran that originate from the Zagros mountain range in Kurdistan and East Azerbaijan provinces. Along the way of Qezel ozan, “Hyrochay”,”Zanjanrood” and “Shahrood” are added to it and arrive to Manjil Dam Lake. From the dam site to the Caspian Sea, the river is called “Sepidroud”.
Qezel ozan River is the only river that originates from Zagros mountain and crossing Alborz mountain, finally flows into the Caspian Sea. Its length is 670 km measured.
Qezel ozan is a phrase in Turkish language and composed of two sections, “Qezel” and “Ozan”. It means “the Great and glorious river”.
The above picture shows a view of river valley in the north-east of Mianeh city and North of Qaflankuh mountain. In this area, the river passes from the West towards the East in a deep canyon (700 meters) and among of the maze of rocks and resistant layers. In this area, slopes are steep and cliff form and end to sharp peak, at the highest points. At the heart of this rough topography, the river has dug its bed as Entrenched meander.
In this area, thick and well bedded extrusive igneous rocks and Pyroclastic rocks, with low angle to the south are build all of ridges of area. This river valley caused by tectonic and erosion has been created over a long time and During long time, the river flows in it.

Keywords: Alborz Mountain , Entrenched meander , Igneous , Iran Geology , Iran Geotourism , Mianeh , Pyroclastic , Qezel ozan , River ,  River valley , rock , Zagros Mountain , Zamin gasht , Ghezel ozan

Maharlu lake

Maharlu Lake is located at 18km of south-east of Shiraz at an altitude of 1560 meters above the sea level and it is one of the tourist and resorts areas due to the proximity to the metropolitan city of Shiraz. This lake is supplied by three rivers, Khoshk, Hamzeh, and Sarvestan and also surrounding mountains runoff. This lake is 28 km long, 10 to 15 km wide and does not have a way to the open sea. Since the rate of evaporation in Maharlu Lake is high, salt covers a layer of it and water is only in the northern and central parts of it with very little depth and high salinity.

One of the interesting phenomena of this lake is the phenomenon of red tide. Red tides are a type of algae that are resistant to salt and when salinity rises, they growth more. The excessive proliferation of these organisms causes increasing the density of algae and place in a layer mode which prevents the air exchange and finally reduction of oxygen to water. In this condition, they produce some of the toxic organisms that are a potential risk for aquatic and hence, they endanger the aquatic and animals life that are adjacent the lake.

Maximum depth of this lake is 3meters so its amount of evaporation is high and this cause a part of lake bed to be covered with a layer of salt, of course the existence of chalky sediments of sachun formation and two salt domes in the east of the lake have considerably effect on its extreme saltiness.

Maharlu lake is a syncline-like subsidence with north west – south east trend and young and seismic sarvestan fault passes through it. It seems that this fault movements, especially in Late Pleistocene, has cause of syncline-like subsidence.

Image is looking to the East. In this Image, part of Maharlu lake, Shiraz-Goshnekan road, Lake Coastal Plain, Limestone mountains overlooking the lake (Asmari formation) and some abandoned buildings are seen.