Why Scientists Started Watching Ohio Closely

Ohio looks ordinary from above, but scientists are building a very different map of what lies underneath. USGS records show 160-plus felt earthquakes since 1776, including a damaging magnitude 5.4 event in 1937. Lost river systems, massive groundwater reserves, caves, abandoned mines, and ancient rock formations extending beneath Lake Erie. Today on DiscoverTube, we're uncovering 20 discoveries beneath Ohio. 1. OHIO HAS RIVERS THAT NO LONGER EXIST ON THE SURFACE Long before today's Ohio River system existed, the Tayes River crossed Ohio from near Portsmouth, flowing north and then northwest across the state. Then, continental glaciers arrived. They blocked the ancient drainage network and buried sections beneath enormous quantities of sediment. In parts of southwestern and central Ohio, USGS research shows these buried valleys contain 200 to more than 600 feet of glacial deposits. That's enough material to bury a 50-story building. Yet the vanished valleys still matter. USGS hydrogeologist Stanley E. Norris identified the buried Tayes Valley system as one of Ohio's important groundwater settings. Historical USGS data estimated statewide groundwater use at roughly 650 million gallons per day. And scientists have literally used seismic methods to find these invisible valleys. USGS researchers R.E. Warwick and J.D. Winslow demonstrated that seismic surveys could determine bedrock depth beneath glacial sediment where almost no surface evidence of the old valleys remained. So beneath modern roads and farmland is the outline of a river system that disappeared during the Ice Age. No visible river. In some places, more than 600 feet of sediment above its ancient valley. Yet groundwater still follows parts of this buried landscape. And the Tayes wasn't the only valley the glaciers transformed. 2. SOME OF OHIO'S BEST AQUIFERS ARE BURIED ICE-AGE VALLEYS Ohio's groundwater isn't distributed evenly. Some of the state's largest supplies occur where ancient valleys became filled with permeable glacial sand and gravel. Historical USGS estimates placed Ohio groundwater use at approximately 650 million gallons per day. That's close to 1,000 Olympic swimming pools every day. USGS identified watercourse aquifers composed largely of glacial sand and gravel as some of the state's most productive groundwater sources. Around Columbus, researchers found particularly productive glacial deposits beneath buried valleys associated with the Scioto River and Big Walnut Creek. Measured horizontal hydraulic conductivity in the Glacial Drift Aquifer ranged from approximately 30 to 375 feet per day. That enormous range demonstrates how different Ohio can become underground. One layer barely transmits water. Another acts almost like a buried gravel highway. And near Lake Erie, USGS scientists have drilled and monitored hundreds of wells to understand where that hidden water is going. 3. SCIENTISTS USED MORE THAN 200 WELLS TO MAP HIDDEN WATER NEAR LAKE ERIE BETWEEN CLEVELAND AND CONNAUGHT The visible shoreline tells only part of the story. Groundwater moves beneath it. During a major USGS investigation, scientists examined an area approximately 60 miles long and 10 miles inland along Lake Erie. They measured groundwater levels in 202 wells and specific conductance in 59 of them. The wells penetrated glacial deposits and zones near the underlying shale. Why so many measurements? Because groundwater can move towards streams, pumping wells, wetlands, and Lake Erie itself. Every additional monitoring well gives scientists another window into the underground flow system. And Lake Erie's surrounding basin is enormous. The broader Lake Erie-Lake St. Clair drainage basin covers about 22,300 square miles and contained roughly 10.4 million people by 1990. But water isn't the only thing hidden underneath northern Ohio. Far below Lake Erie itself are tunnels large enough for industrial vehicles. 4. THERE ARE SALT MINES BENEATH LAKE ERIE Drive through Cleveland and Lake Erie looks like an uninterrupted sheet of water. Far below it are enormous deposits of rock salt. The salt is the residue of an ancient geological world. Hundreds of millions of years ago, seawater repeatedly entered and evaporated from basins covering this region. Water disappeared. Salt remained. Later sediments buried those evaporite deposits beneath younger rock. Today, mining operations have followed those layers underground and beneath Lake Erie. The result is one of Ohio's strangest geological contrasts. ABOVE, ONE OF EARTH'S LARGEST FRESHWATER SYSTEMS. BELOW, ENORMOUS DEPOSITS CREATED BY ANCIENT SALTWATER. MODERN OHIO IS ESSENTIALLY SITTING BETWEEN TWO COMPLETELY DIFFERENT SEAS SEPARATED BY GEOLOGICAL TIME. BUT NOT EVERY UNDERGROUND OPENING IN OHIO WAS EXCAVATED BY HUMANS. SOME WERE DISSOLVED NATURALLY. 5. WESTERN OHIO IS BUILT ON ROCK THAT CAN DEVELOP SINKHOLES Parts of Western Ohio are underlain by limestone and dolomite. Those rocks can dissolve when slightly acidic groundwater enters fractures. The process creates karst, sinkholes, caves, springs, underground drainage. The surface may remain normal while openings slowly enlarge below it. Eventually, some cavities become large enough to affect the ground above. OHIO THEREFORE HAS TWO COMPLETELY DIFFERENT TYPES OF HIDDEN VOIDS. SOME ARE NATURAL CAVES DISSOLVED OVER THOUSANDS OF YEARS. OTHERS ARE HUMAN-MADE MINES EXCAVATED IN ONLY DECADES. AND TELLING THE DIFFERENCE MATTERS WHEN THE GROUND BEGINS MOVING. 6. OHIO HAS GROUND THAT CAN COLLAPSE ABOVE OLD MINES. OHIO'S INDUSTRIAL HISTORY DIDN'T END WHEN INDIVIDUAL MINES CLOSED. THE EMPTY SPACE REMAINED. UNDERGROUND MINING CAN LEAVE ROOMS, PILLARS, SHAFTS, AND TUNNELS BENEATH MODERN LANDSCAPES. AS SUPPORTS DETERIORATE OR ROOFS FAIL, MOVEMENT CAN PROPAGATE UPWARD. EVENTUALLY, THE SURFACE CAN SUBSIDE. THE UNSETTLING PART IS TIMING. A MINE MAY CLOSE. BUILDINGS CHANGE. ROADS ARE CONSTRUCTED. DECADES PASS. THEN, MOVEMENT UNDERGROUND BEGINS AFFECTING THE SURFACE. IT'S A DELAYED GEOLOGICAL CONSEQUENCE OF INDUSTRIAL HISTORY. OHIO'S LANDSCAPE THEREFORE CONTAINS CAVITIES FORMED BY WATER AND CAVITIES FORMED BY HUMANS. BUT THE STATE HAS ANOTHER HIDDEN FEATURE THAT CAN'T BE SEEN EVEN WHEN YOU'RE STANDING DIRECTLY ABOVE IT. STRESS. 7. OHIO HAS RECORDED MORE THAN 160 FELT EARTHQUAKES. OHIO ISN'T CALIFORNIA, BUT IT ISN'T EARTHQUAKE-FREE. USGS RESEARCHERS RICHARD DART AND MICHAEL HANSEN COMPILED OHIO'S SEISMIC HISTORY FROM WRITTEN ACCOUNTS AND INSTRUMENTAL MEASUREMENTS. THEIR RECORD DOCUMENTED MORE THAN 160 FELT EARTHQUAKES BETWEEN 1776 AND 2007. MOST CAUSED NO SIGNIFICANT DAMAGE. BUT 15 OHIO EARTHQUAKES PRODUCED PROPERTY DAMAGE AND SOME MINOR INJURIES. THAT CHANGES THE PICTURE. OHIO DOESN'T EXPERIENCE EARTHQUAKES EVERY DAY THAT RESIDENTS NOTICE. BUT OVER HISTORICAL TIME, THE STATE HAS REPEATEDLY MOVED ENOUGH FOR PEOPLE TO FEEL IT. BEFORE MODERN SEISMOMETERS, SCIENTISTS RECONSTRUCTED THOSE EVENTS FROM LETTERS, DIARIES, NEWSPAPERS AND REPORTS. TODAY, INSTRUMENTS CAN DETECT EARTHQUAKES FAR TOO SMALL FOR HUMANS TO NOTICE. AND ONE PART OF WESTERN OHIO HAS ALREADY DEMONSTRATED WHAT A SUBSTANTIALLY LARGER EARTHQUAKE CAN DO. 8. THE 1937 EARTHQUAKE DAMAGED AN OHIO TOWN. ON MARCH 9, 1937, WESTERN OHIO SHOOK. THE EARTHQUAKE STRUCK NEAR ANNA. USGS ESTIMATES ITS MAGNITUDE AT APPROXIMATELY 5.4, MAKING IT THE LARGEST HISTORICAL EARTHQUAKE DOCUMENTED WITHIN OHIO. BUILDINGS WERE DAMAGED IN ANNA AND SURROUNDING COMMUNITIES. CHIMNEYS FELL. WALLS CRACKED. SCHOOLS WERE AFFECTED. MAGNITUDE 5.4 DOESN'T SOUND EXTRAORDINARY BESIDE A MAGNITUDE 7 OR MAGNITUDE 8 EARTHQUAKE. BUT MAGNITUDE IS LOGARITHMIC. A MODERATE EARTHQUAKE OCCURRING BENEATH POPULATED AREAS CAN STILL PRODUCE SIGNIFICANT DAMAGE. AND OHIO'S OLDER CRUST CAN TRANSMIT SEISMIC WAVES EFFICIENTLY ACROSS CONSIDERABLE DISTANCES. THE ANNA EARTHQUAKE PERMANENTLY DESTROYED THE IDEA THAT DAMAGING EARTHQUAKES SIMPLY DON'T HAPPEN HERE. BUT WESTERN OHIO ISN'T THE ONLY PART OF THE STATE WHERE SCIENTISTS RECORD SHAKING. 9. NORTHEAST OHIO HAS ITS OWN EARTHQUAKE HISTORY. OHIO EARTHQUAKES DON'T ALL CLUSTER AROUND ANNA. NORTHEASTERN OHIO HAS ALSO EXPERIENCED REPEATED SEISMIC ACTIVITY. THAT'S ESPECIALLY INTERESTING BECAUSE THIS REGION CONTAINS CLEVELAND, LAKE ERIE INFRASTRUCTURE, INDUSTRY AND MILLIONS OF RESIDENTS ACROSS THE WIDER METROPOLITAN AREA. SCIENTISTS DISTINGUISH NATURAL EARTHQUAKES FROM OTHER VIBRATION SOURCES BY STUDYING SEISMIC WAVEFORMS, DEPTH, TIMING AND LOCATION. MODERN INSTRUMENTS CAN DETECT MOVEMENTS NOBODY FEELS. THAT GIVES RESEARCHERS A COMPLETELY DIFFERENT OHIO MAP. NOT COUNTY LINES, NOT HIGHWAYS, EPICENTERS, CLUSTERS, FAULT ORIENTATIONS AND ACCUMULATED SEISMIC HISTORY. USGS BEGAN PUBLISHING DEDICATED SEISMICITY MAPS OF OHIO DECADES AGO, COMPILING BOTH HISTORICAL AND INSTRUMENTALLY DETECTED EVENTS. OHIO MAY LOOK MOTIONLESS, THE INSTRUMENTS SAY OTHERWISE. AND IF YOU'RE ENJOYING THESE HIDDEN GEOLOGICAL STORIES, SUBSCRIBE TO DISCOVERTUBE, BECAUSE EARTHQUAKES ARE ONLY ONE REMNANT OF OHIO'S ANCIENT PAST. THE NEXT ONE CHANGED ALMOST THE ENTIRE STATE. 10. A WALL OF ICE ONCE COVERED MOST OF OHIO. TO UNDERSTAND MODERN OHIO, REMOVE THE FARMS, CITIES, HIGHWAYS AND LAKE ERIE SHORELINE, THEN COVER MUCH OF THE STATE IN ICE. DURING REPEATED ICE-AGE GLACIATIONS, CONTINENTAL GLACIERS ADVANCED FROM THE NORTH. THESE WEREN'T MOUNTAIN GLACIERS OCCUPYING NARROW VALLEYS. THEY WERE PARTS OF CONTINENTAL ICE SHEETS. THEY SCRAPED BEDROCK, MOVED BOULDERS, BURIED VALLEYS, REDIRECTED RIVERS, DEPOSITED ENORMOUS QUANTITIES OF SEDIMENT AND COMPRESSED THE LANDSCAPE BENEATH THEIR WEIGHT. MUCH OF OHIO'S MODERN SOIL, DRAINAGE, GROUNDWATER AND TOPOGRAPHY STILL REFLECTS THOSE EVENTS. THE GLACIERS ARE GONE. THEIR GEOLOGICAL INFRASTRUCTURE REMAINS. THAT INCLUDES THE SEDIMENTS UNDERNEATH CITIES, THE MATERIAL SURROUNDING AQUIFERS, AND THE LANDSCAPE CONTROLLING WHERE MODERN RIVERS FLOW. BUT ONE FEATURE LEFT BEHIND BY THE ICE BECAME FAR LARGER THAN ANY BURIED VALLEY. LAKE ERIE WOULDN'T EXIST IN ITS MODERN FORM WITHOUT GLACIATION. ICE REPEATEDLY EXCAVATED AND MODIFIED THE BASIN. THEN, AS THE GLACIERS RETREATED, MELTWATER OCCUPIED CHANGING DEPRESSIONS. THE SHORELINE MOVED THROUGH DIFFERENT STAGES BEFORE APPROACHING THE LAKE WE RECOGNIZE TODAY. LAKE ERIE IS RELATIVELY SHALLOW COMPARED WITH THE OTHER GREAT LAKES. THAT MAKES IT PARTICULARLY RESPONSIVE TO WIND, STORMS, SEDIMENT MOVEMENT AND BIOLOGICAL CHANGE. BUT UNDERNEATH THE MODERN LAKE ARE OLDER SEDIMENTS, BEDROCK, GROUNDWATER SYSTEMS AND GEOLOGICAL EVIDENCE FROM ENVIRONMENTS THAT EXISTED BEFORE TODAY'S SHORELINE STABILIZED. OHIO THEREFORE DOESN'T SIMPLY BORDER LAKE ERIE. NORTHERN OHIO SITS AT THE EDGE OF AN ENORMOUS POSTGLACIAL SYSTEM THAT CONTINUES INFLUENCING GROUNDWATER, EROSION, WEATHER, ECOSYSTEMS AND INFRASTRUCTURE. AND UNDERNEATH THAT FRESHWATER IS EVIDENCE OF AN OCEAN THAT VANISHED HUNDREDS OF MILLIONS OF YEARS EARLIER. FORGET MODERN OHIO'S LATITUDE. TRAVEL HUNDREDS OF MILLIONS OF YEARS INTO THE PAST AND THE REGION LOOKED COMPLETELY DIFFERENT. WARM, SHALLOW SEAS REPEATEDLY COVERED PARTS OF WHAT WOULD EVENTUALLY BECOME OHIO. MARINE ORGANISMS LIVED WHERE CITIES AND FARMS STAND TODAY. THEIR REMAINS BECAME INCORPORATED INTO LIMESTONE, SHALE AND OTHER SEDIMENTARY ROCKS. THAT'S WHY OHIO CAN CONTAIN MARINE FOSSILS DESPITE BEING HUNDREDS OF MILES FROM THE ATLANTIC OCEAN. BRACHIOPODS, CORALS, CRINOIDS, TRILOBITES, OTHER ORGANISMS FROM ANCIENT SEAS. A ROCK COLLECTED BESIDE AN OHIO ROAD CAN CONTAIN EVIDENCE OF AN OCEAN THAT DISAPPEARED HUNDREDS OF MILLIONS OF YEARS BEFORE HUMANS EXISTED. BUT THOSE ANCIENT SEAS LEFT BEHIND MORE THAN FOSSILS. THEY ALSO HELPED CREATE THE SHALE THAT CAUSES A MODERN PROBLEM INSIDE OHIO HOMES. 13. OHIO SHALE CONTAINS URANIUM AND THAT CAN PRODUCE RADON. ONE OF OHIO'S MOST IMPORTANT GEOLOGICAL FORMATIONS IS LITERALLY NAMED AFTER THE STATE, THE OHIO SHALE. THIS UPPER DEVONIAN ROCK CONTAINS ORGANIC MATERIAL AND VARYING CONCENTRATIONS OF URANIUM. AS URANIUM NATURALLY DECAYS, IT EVENTUALLY PRODUCES RADON GAS. RESEARCH SUMMARIZED BY EPA EXAMINED THE CONNECTION BETWEEN OHIO SHALE GEOLOGY AND INDOOR RADON ACROSS AREAS INCLUDING ASHTABULA, CAYAHOGA, ERIE HURON, FRANKLIN, PIKE, AND LOGAN COUNTIES. RESEARCHERS FOUND THAT RADON RELEASED FROM THE OHIO SHALE WAS DIRECTLY RELATED TO URANIUM CONCENTRATION, WHICH ITSELF WAS CONNECTED WITH ORGANIC CONTENT IN THE SHALE. THIS IS GEOLOGY CROSSING DIRECTLY INTO MODERN LIFE. A ROCK FORMED IN AN ANCIENT MARINE ENVIRONMENT CAN INFLUENCE THE CONCENTRATION OF A RADIOACTIVE GAS INSIDE A BASEMENT HUNDREDS OF MILLIONS OF YEARS LATER. EPA CONTINUES TO MAINTAIN RADON ZONE INFORMATION AND OHIO-SPECIFIC RADON RESOURCES. THE ANCIENT SEA IS GONE. ITS CHEMISTRY ISN'T. 14. CINCINNATI SITS BESIDE ONE OF AMERICA'S FAMOUS FOSSIL REGIONS. SOUTHWESTERN OHIO TELLS ANOTHER ANCIENT SEA STORY. THE CINCINNATI REGION IS INTERNATIONALLY KNOWN FOR FOSSIL-RICH ORDOVICIAN ROCKS. LAYERS EXPOSED IN ROAD CUTS, STREAM VALLEYS AND HILLSIDES PRESERVE MARINE ORGANISMS FROM HUNDREDS OF MILLIONS OF YEARS AGO. THE QUANTITY CAN BE STARTLING. IN SOME EXPOSURES, FOSSILS AREN'T RARE OBJECTS REQUIRING CAREFUL EXCAVATION. THEY'RE EVERYWHERE. THAT'S BECAUSE CINCINNATI WASN'T ALWAYS INLAND. THE SEDIMENT BENEATH THE REGION ACCUMULATED IN A COMPLETELY DIFFERENT ENVIRONMENT. MODERN NEIGHBORHOODS OCCUPY A LANDSCAPE CONSTRUCTED PARTLY FROM THE REMAINS AND SEDIMENTS OF ANCIENT MARINE ECOSYSTEMS. BUT OHIO'S FOSSIL HISTORY BECOMES EVEN STRANGER WHEN YOU MOVE FROM ORDINARY ANCIENT SEAS TOWARD ONE UNUSUAL CIRCULAR STRUCTURE. 15. THE SERPENT MOUND REGION CONTAINS A GEOLOGICAL MYSTERY. SOUTHERN OHIO CONTAINS ONE OF THE STATE'S MOST UNUSUAL CIRCULAR GEOLOGICAL STRUCTURES NEAR SERPENT MOUND. THE DISTURBED ROCK PATTERN HAS ATTRACTED SCIENTIFIC INVESTIGATION BECAUSE ITS GEOLOGY DIFFERS DRAMATICALLY FROM SURROUNDING HORIZONTAL SEDIMENTARY LAYERS. RESEARCHERS HAVE DEBATED ITS ORIGIN HISTORICALLY, WITH IMPACT-RELATED INTERPRETATIONS BECOMING AN IMPORTANT PART OF THE SCIENTIFIC DISCUSSION. THE FEATURE DEMONSTRATES A BROADER POINT. OHIO'S SEDIMENTARY ROCKS MAY APPEAR ORDERLY ACROSS LARGE DISTANCES. THEN, SUDDENLY, THOSE LAYERS BECOME FRACTURED, DISPLACED OR STRUCTURALLY DISTURBED. SOMETHING HAPPENED, AND GEOLOGISTS RECONSTRUCT THAT EVENT FROM THE GEOMETRY PRESERVED UNDERGROUND. IT'S GEOLOGICAL DETECTIVE WORK. THE EVIDENCE IS ROCK. THE CRIME SCENE CAN BE HUNDREDS OF MILLIONS OF YEARS OLD. COLUMBUS IS BUILT ABOVE GLACIAL GROUNDWATER. OHIO'S CAPITAL PROVIDES A PERFECT EXAMPLE OF HOW ANCIENT GEOLOGY SUPPORTS A MODERN CITY. USGS RESEARCHERS STUDYING THE SOUTHWELL FIELD NEAR COLUMBUS FOUND PRODUCTIVE GLACIAL-DRIFT AQUIFERS ASSOCIATED WITH BURIED VALLEYS BENEATH THE SIOTO RIVER AND BIG WALNUT CREEK. HYDRAULIC CONDUCTIVITY RANGED FROM APPROXIMATELY 30 TO 375 FEET PER DAY IN THE GLACIAL AQUIFER. RECHARGE ESTIMATES RANGED FROM ABOUT 4 TO 12 INCHES PER YEAR, DEPENDING ON LOCATION. THE SYSTEM RECEIVES WATER FROM PRECIPITATION, REGIONAL GROUNDWATER MOVEMENT, AND INDUCED INFILTRATION FROM STREAMS. IN OTHER WORDS, COLUMBUS DOESN'T SIT ABOVE ONE SIMPLE UNDERGROUND RESERVOIR. IT'S POSITIONED OVER A MOVING SYSTEM WHERE SURFACE WATER AND GROUNDWATER INTERACT. RAIN FALLING TODAY CAN EVENTUALLY BECOME PART OF THAT HIDDEN CIRCULATION, AND THE GLACIAL VALLEYS GUIDING IT ARE REMNANTS OF A LANDSCAPE FAR OLDER THAN THE CITY ABOVE THEM. 17. LAKE ERIES GROUNDWATER DOESN'T STOP AT THE SHORELINE A shoreline looks like a boundary. Hydrologically, it isn't always one. GROUNDWATER BENEATH NORTHERN OHIO CAN CONTINUE MOVING TOWARD LAKE ERIE. THAT'S WHY USGS RESEARCHERS MEASURED MORE THAN 200 WELLS ACROSS A CORRIDOR EXTENDING ROUGHLY 60 MILES BETWEEN CLEVELAND AND CONNAUGHT. THE GOAL WAS TO UNDERSTAND GROUNDWATER LEVELS, FLOW, AND WATER CHEMISTRY IN UNCONSOLIDATED AQUIFERS NEAR THE LAKE. WATER UNDERGROUND DOESN'T CARE WHERE OHIO ENDS AND LAKE ERIE BEGINS. IT FOLLOWS HYDRAULIC GRADIENTS. THIS CREATES CONNECTIONS BETWEEN RAINFALL, WELLS, STREAMS, SHORELINE SEDIMENTS, AND THE LAKE ITSELF. SO WHEN SCIENTISTS INVESTIGATE LAKE ERIE WATER QUALITY, THE VISIBLE LAKE IS ONLY ONE COMPONENT. SOME OF THE SYSTEM IS MOVING BENEATH THEIR FEET. 18. OHIO'S LANDSCAPE STILL CONTAINS BURIED GLACIAL CLUES MUCH OF OHIO'S MODERN APPEARANCE IS DECEPTIVELY SMOOTH. AGRICULTURE HAS MODIFIED FIELDS. CITIES COVER SEDIMENT. ROADS CUT ACROSS OLD TERRAIN. BUT UNDERNEATH ARE DEPOSITS LEFT BY MULTIPLE GLACIAL ENVIRONMENTS. TILL. SAND. GRAVEL. LAKE SEDIMENT. OUTWASH. BURIED VALLEYS. USGS DESCRIBES THE ENTIRE LAKE ERIE LAKE SAINT CLARE BASIN AS BEING COVERED BY PLEISTOCENE DEPOSITS. WITH BURIED RIVER VALLEYS FILLED BY COMBINATIONS OF LAKE, RIVER AND COARSE GLACIAL SEDIMENTS. THOSE MATERIALS AREN'T SIMPLY REMNANTS. THEY DETERMINE WHERE GROUNDWATER MOVES. WHERE WELLS ARE PRODUCTIVE. HOW CONTAMINANTS TRAVEL. AND HOW CONSTRUCTION INTERACTS WITH THE SUBSURFACE. THE ICE AGE ENDED THOUSANDS OF YEARS AGO. OHIO STILL RUNS ON SOME OF THE INFRASTRUCTURE IT LEFT BEHIND. OHIO'S UNDERGROUND MAP KEEPS GETTING MORE DETAILED. FOR GENERATIONS, GEOLOGISTS RECONSTRUCTED OHIO'S SUBSURFACE USING EXPOSED ROCK, QUARRIES, MINES, WELLS, FOSSILS AND SURFACE LANDFORMS. NOW, RESEARCHERS CAN COMBINE THOSE RECORDS WITH DIGITAL ELEVATION MODELS, SEISMIC INSTRUMENTS, GROUNDWATER MONITORING, GEOPHYSICAL MEASUREMENTS AND INCREASINGLY DETAILED GEOLOGICAL DATABASES. A BURIED VALLEY INVISIBLE AT GROUND LEVEL CAN EMERGE FROM WELL RECORDS. A TINY EARTHQUAKE NOBODY FEELS APPEARS ON A SEISMIC NETWORK. GROUNDWATER MOVEMENT BECOMES VISIBLE THROUGH HUNDREDS OF MEASUREMENTS. ROCK HIDDEN BENEATH GLACIAL SEDIMENT CAN BE RECONSTRUCTED FROM DRILLING. EVERY NEW DATA SET ADDS ANOTHER LAYER. THE RESULT ISN'T ONE UNDERGROUND OHIO MAP, IT'S MANY. AND THE MORE THOSE MAPS OVERLAP, THE LESS ORDINARY OHIO BECOMES. PUT EVERYTHING TOGETHER. OHIO HAS EXPERIENCED MORE THAN 160 FELT EARTHQUAKES IN ITS RECORDED SEISMIC HISTORY THROUGH 2007. A MAGNITUDE 5.4 EARTHQUAKE DAMAGED WESTERN OHIO IN 1937. HISTORICAL USGS ESTIMATES PLACED GROUNDWATER USE AROUND 650 MILLION GALLONS PER DAY. BURIED GLACIAL VALLEYS STILL CARRY WATER BENEATH MODERN COMMUNITIES. THE ANCIENT TAYS DRAINAGE SYSTEM SURVIVES UNDERGROUND EVEN THOUGH ITS SURFACE RIVER DISAPPEARED. LAKE ERIE OCCUPIES A LANDSCAPE TRANSFORMED BY CONTINENTAL ICE. SALT DEPOSITS PRESERVE EVIDENCE OF ANCIENT SEAS. OHIO SHALE CONNECTS DEVONIAN GEOLOGY WITH MODERN RADON CONCERNS. FOSSILS REVEAL OCEANS WHERE CITIES NOW STAND. NATURAL CAVES AND ABANDONED MINES CREATE COMPLETELY DIFFERENT TYPES OF UNDERGROUND SPACE. AND SEISMIC INSTRUMENTS CONTINUE LISTENING FOR MOVEMENT INSIDE ROCK MOST OHIO RESIDENTS NEVER SEE. THAT'S WHAT MAKES OHIO DIFFERENT FROM THE STATES WE'VE EXPLORED BEFORE ON DISCOVERTUBE. THERE ISN'T ONE GIANT GEOLOGICAL MYSTERY DOMINATING EVERYTHING. OHIO'S STORY IS ABOUT BURIED LANDSCAPES STACKED ON TOP OF ONE ANOTHER. AN ANCIENT OCEAN. A VANISHED RIVER NETWORK. AN ICE-AGE LANDSCAPE. MODERN GROUNDWATER. INDUSTRIAL MINES. AND AN ACTIVE CRUST. EACH GENERATION OF SCIENTISTS HAS BEEN ABLE TO SEE A LITTLE DEEPER INTO THAT STACK. SO HERE'S THE FINAL QUESTION. IF AN ENTIRE RIVER SYSTEM CAN DISAPPEAR BENEATH OHIO AND STILL CARRY GROUNDWATER THOUSANDS OF YEARS LATER, WHAT ELSE COULD SCIENTISTS EVENTUALLY FIND HIDDEN BENEATH THE STATE? TELL US IN THE COMMENTS AND SUBSCRIBE TO DISCOVERTUBE FOR THE NEXT INVESTIGATION. BECAUSE OHIO MAY LOOK ORDINARY FROM THE SURFACE, UNDERGROUND, ALMOST NOTHING ABOUT IT IS.