NASA Captures the Eye of the Sahara: The Richat Structure

Seeing those crisp satellite images of the Richat Structure from space this week got me thinking about how we perceive scale and pattern in our own backyards. That massive, nearly 40-kilometer-wide bullseye etched into the Sahara Desert—visible only from orbit—reminds me how easily we overlook the profound geological stories written into the landscapes we traverse daily. While Mauritania’s Adrar Plateau feels worlds away, the same forces shaping those concentric rings—erosion, uplift, the slow dance of rock and time—are quietly at work beneath our feet, even in places as seemingly stable as the suburban sprawl ringing major cities.

Accept the Chicago metropolitan area, for instance. Beneath the grid of expressways and neighborhood streets lies a complex glacial legacy. The Wisconsin Glacier’s retreat over 10,000 years ago didn’t just leave flat prairie. it dumped moraines, carved out lake basins that became Lake Michigan, and left ridges like the Valparaiso and Tinley Moraines that still subtly dictate where water flows and where neighborhoods sit. Just as the Richat Structure’s rings reveal differing erosion rates in sedimentary and igneous rock layers, Chicago’s landscape tells a story of varying glacial till—some areas hard-packed and resistant, others prone to swelling clay that shifts foundations after heavy rains. It’s a slower, less conspicuous process than the Saharan uplift Voiland described, but no less real for homeowners noticing cracks in basement walls or municipalities managing stormwater flow.

This connection between deep time and daily life isn’t just academic. Consider how the United States Geological Survey (USGS) operates its Chicago Lake Michigan Field Station, monitoring groundwater levels and land subsidence in real time. Or how the City of Chicago’s Department of Water Management constantly models how glacial aquifers interact with aging infrastructure—a direct descendant of the kind of landscape analysis NASA applies to the Richat Structure using Landsat 8 and 9 data. Even the Forest Preserves of Cook County, managing over 70,000 acres of varied terrain, rely on paleoecological studies (think pollen cores from ancient wetlands) to understand how post-glacial vegetation shifts mirror today’s climate challenges—a parallel to how scientists study the Richat Structure’s exposed rock layers to decode Earth’s history.

What struck me most from the NASA Earth Observatory’s April 16 Image of the Day wasn’t just the visual spectacle, but the emphasis on how natural forces—not human activity—dominate that Mauritanian landscape. Wind sculpting dunes, ancient water carving now-dry channels… it’s a humbling counterpoint to our urban obsession with control. Yet here in Chicagoland, we see the same tension: the Chicago River’s flow reversed not by conquest, but by engineering working *with* continental divides; the lake-effect snow that buries neighborhoods stems from temperature contrasts the lake itself creates. Recognizing these deep-set patterns doesn’t indicate surrendering to nature—it means designing smarter, whether it’s permeable pavements in Evanston that mimic natural infiltration or green roofs in the Loop that manage heat islands by echoing prairie evapotranspiration.

Given my background in environmental systems analysis, if this trend of looking beneath the surface impacts you in the Chicago area, here are the three types of local professionals you need to understand your property’s hidden story:

• Geotechnical Engineers Specializing in Glacial Terrain: Appear for consultants with specific experience interpreting Illinois State Geological Survey (ISGS) surficial geology maps and boring logs. They should reference local formations like the Wilmette Gravel or Joliet Formation and understand how lacustrine soils near ancient Lake Chicago outlets behave differently than till plains—critical for assessing foundation risk or infiltration potential for rain gardens.
• Landscape Architects Focused on Native Ecological Restoration: Seek professionals who partner with institutions like the Chicago Botanic Garden’s Plants of Concern program or use Audubon Great Lakes’ native plant databases. Their work should demonstrate knowledge of how glacial topography influences hydrology—like designing swales that follow ancient meltwater channels or selecting deep-rooted prairie species suited to specific moraine soil types to stabilize slopes.
• Certified Arborists with Urban Soil Expertise: Prioritize arborists certified by the ISA who utilize tools like air spades to examine root zones without damage and reference the Morton Arboretum’s urban soil studies. They should assess how compacted glacial clay or fill material affects tree health and prescribe solutions—like vertical mulching or structural soil—based on site-specific soil texture reports, not generic advice.

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