Unraveling Nature's Layers and Human Footprints
Discover how scientists are playing the role of geological detectives, using earth science methods to solve a captivating puzzle: which terraces are natural wonders and which are the legacy of ancient human ingenuity.
Lake Van, a vast inland sea in Eastern Anatolia, Turkey, is not only the world's largest soda lake but also a breathtaking open-air archive of history. Its shores are etched with a series of stepped terraces, resembling a giant's staircase. For centuries, these terraces have silently witnessed the ebb and flow of both water and human civilization.
Which of these terraces are natural wonders crafted by climate and tectonics, and which are the legacy of ancient human ingenuity?
This article explores how scientists are playing the role of geological detectives, using earth science methods to solve this captivating puzzle.
To understand the terraces, one must first understand the lake. Lake Van is a tectonic giant, formed by the subsidence of a massive block of the Earth's crust over 600,000 years ago in a region squeezed by the collision of the Eurasian and Afro-Arabian plates3 7 .
This tectonic activity, combined with volcanism from nearby mountains like Nemrut and Süphan, set the stage for the lake's dramatic history7 .
Crucially, Lake Van is a closed basin with no natural outlet; its water level is a delicate balance between incoming precipitation and river flow versus outgoing evaporation5 .
This makes it an exceptionally sensitive recorder of environmental change, preserving clues about past climates and human activities in its geological formations.
The terraces encircling Lake Van are essentially former shorelines, now high and dry. However, they come from two very different origins:
These are the product of colossal geological forces. During past ice ages, when climates were colder and drier, Lake Van's level dropped dramatically—at one point, it was about 200 meters below its current level5 6 .
During warmer, wetter interglacial periods, the lake swelled, reaching up to 105 meters above today's shore5 7 . Each time the lake stabilized at a certain level, it carved a terrace.
Furthermore, the entire region is being actively pushed upward by tectonic forces, literally lifting these ancient shorelines out of the water3 .
For millennia, humans have looked at the undulating, erosion-prone natural slopes and seen an opportunity. Starting as early as the Urartian Period (800-400 BC), people began to reconstruct the landscape1 .
They built retaining walls and carved the land into flat, cultivable terraces to combat erosion and create arable land in a semi-arid region with a short growing season.
These human-modified landscapes are known as anthroscapes—distinct ecosystems shaped by sustained human activity1 .
| Feature | Natural Terraces | Man-Made Terraces (Anthroscapes) |
|---|---|---|
| Formation Cause | Climate change (lake level fluctuations), tectonic uplift | Human agricultural engineering |
| Physical Shape | Undulating, irregular slopes | Distinctly flat cultivation surfaces with retaining walls |
| Soil Properties | Natural soil profiles developed over millennia | Significantly altered physical, chemical, and biological properties1 |
| Key Indicator | Found at consistent elevations across wide areas | Patterned structure, evidence of wall foundations, and proximity to ancient settlements |
So, how do researchers tell these nearly identical landforms apart? They rely on a sophisticated toolkit of earth science methods.
The first step is always a detailed survey. Scientists use tools like total stations to create precise elevation profiles of the terraces3 .
To pin down when a terrace was formed, researchers use radiometric dating. By dating shells or organic material found within the terrace sediments, they can determine its age.
Perhaps the most revealing method is a detailed analysis of the soil itself. A landmark study compared soil profiles from natural and man-made terraces and found striking differences1 .
These soil "fingerprints" provide undeniable evidence of human modification, setting the anthroscapes apart from their natural counterparts.
While the methods above help distinguish human-made terraces, another groundbreaking experiment has revolutionized our understanding of the natural forces that created the lake's dramatic history. In 2010, an international team drilled deep sediment cores from the bottom of Lake Van as part of the PALEOVAN project5 6 .
Scientists used a drilling rig on a specially equipped vessel to extract long sediment cores from the lake bed at a site called Ahlat Ridge5 .
From these cores, they carefully extracted porewater—the water trapped between the fine sediment grains. This water is a preserved sample of the ancient lake water from the time the sediment was laid down.
The team then measured the salinity (total dissolved salt content) of these porewater samples, creating a vertical salinity profile through 100 meters of sediment representing 250,000 years5 .
The results were stunning. The salinity profiles showed clear, strong peaks and troughs5 . The principle behind their analysis is beautifully simple: Lake Van is a closed basin, so the total amount of salt dissolved in it is relatively constant over long periods. Therefore, the salinity of the lake water is inversely proportional to the volume of water in the basin6 .
When the porewater salinity was low, it indicated a period of high lake level. A greater volume of water diluted the salt, meaning the lake was full. This confirmed the timing of major transgressions (high stands) around 135,000 and 248,000 years ago5 .
When the porewater salinity was high, it signaled a low lake level. With less water to hold the salt, the concentration rose, pointing to a major regression around 30,000 years ago during the last ice age5 .
| Event | Time (Years Before Present) | Approximate Lake Level Change | Interpreted Climate |
|---|---|---|---|
| Major Transgression | 248,000 | +105 m | Warm, wet interglacial |
| Major Transgression | 135,000 | +105 m | Warm, wet interglacial |
| Major Regression | 30,000 | -200 m | Cold, dry glacial period |
| Terrace Level | Elevation Above Current Lake (meters) | Radiocarbon Age (Years Before Present) |
|---|---|---|
| T2 | +55 - 60 | 30,040 ± 170 to 24,060 ± 100 |
| T4 | +29 - 33 | 6,210 ± 30 |
| T6 | +9 - 15 | 3,680 ± 30 |
| T7 | +3 - 6 | 2,950 ± 30 |
This experiment provided the first quantitative, direct evidence of these enormous lake-level fluctuations, confirming that the natural terraces we see today were formed during these ancient moments of geological drama.
To conduct this kind of research, geoscientists rely on a suite of specialized tools and materials.
| Research Material | Function in Analysis |
|---|---|
| Sediment Cores | Long, cylindrical samples of lake-bottom sediment that serve as the primary archive of past environmental conditions. |
| Porewater Extractor | A device that uses pressure or centrifugation to separate the ancient water from the sediment grains for chemical analysis. |
| Mass Spectrometer | An instrument used for radiometric dating (like AMS-14C) and for analyzing the isotopic composition of elements in water and soil. |
| Total Station | An optical surveying instrument that measures precise angles and distances to create high-resolution topographic maps of terrace formations. |
| Seismic Reflection Profiling | A geophysical method that uses sound waves to image subsurface geological layers beneath the lake floor, revealing buried terraces and faults. |
The work to differentiate Lake Van's terraces is more than an academic exercise; it is a quest for sustainable wisdom. The ancient anthroscapes represent a form of indigenous land management that successfully combated land degradation for centuries1 .
Today, however, both natural and man-made terraces are under threat from modern mismanagement and increasing population pressures1 .
Understanding the unique soil properties and hydrological systems of the sustainable anthroscapes can provide crucial clues for conserving these landscapes today1 . Furthermore, by reconstructing the past, scientists can better model the future.
In the end, the terraces of Lake Van are a powerful reminder that the landscape is a shared manuscript, with its pages written by the forceful hand of nature and meticulously annotated by human culture. By learning to read this manuscript, we not only unlock the secrets of the past but also gain the insight needed to steward this unique environment for generations to come.