Credit XKCD #3221The map above shows how why the various bits of the US landscape are the way they are.The hidden text: ‘Well, there’s speculation that it’s due to a mantle hotspot.’ –a geologist who’s trying to cover up the fact that they didn’t hear your questionAnd for more here’s an explanation from Explain XKCD:LocationDescriptionExplanationAdirondack Mountains???The Adirondack Mountains are made of billion-year-old rock but were uplifted relatively recently, within the last 5–10 million years. They are still rising today despite being far from any plate boundary, forming a dome with no clear tectonic cause.Most of northern conterminous U.S.glaciersDuring the Last Glacial Period, this area was covered by an ice sheet that left its marks on the landscape, in the form of moraines, eskers, glacial erratics, etc. This is most notable in Wisconsin where bluffs were formed due to the glacier movement.Appalachian Mountainscontinents collidingThe Appalachian Mountains formed roughly 480 to 300 million years ago through a series of continent-continent collisions, culminating in the assembly of the supercontinent Pangaea. The primary collision involved ancestral North America (Laurentia) crashing into Gondwana (Africa/South America), resulting in a Himalayan-scale mountain range.Mississippi and Ohio River BasinsriversThe Mississippi River's geology has a complex, 70 million year history involving massive sediment deposition, glacial activity, and tectonic shifting. Formed mostly by melting glaciers ~12,000 years ago, it drains a vast, shifting basin, depositing millions of tons of sediment in a massive delta and creating a vast, shifting alluvial plain. The Ohio River's geology is similar.Southeastern U.S.farmingLandscape changes from cotton production in the United States, due to the presence of the Black Belt. From the perspective of landscape features, it would be more accurate to say that they were caused by "erosion" not "farming". The Atlantic Coastal Plain is made up of sediments and sedimentary rock eroded from the Appalachian Mountains over millions of years. The relatively flat landscape and loose fertile soils make farming both easy and productive respectively. Thus farming is a result of the landscape features, not a cause of them.Southern Floridaongoing disputes between limestone and waterFlorida is a vast karst landscape formed by the dissolution of underground limestone and dolostone bedrock by acidic rainwater, resulting in a terrain characterized by sinkholes, springs, caverns, and disappearing streams. This soluble bedrock, formed from ancient marine deposits, covers much of the state, directly connecting surface water to the Floridian aquifer system.Southern Missouri / Northern ArkansasgeologyThe Ozark Mountains, which are composed primarily of ancient limestone and dolomite, form a rugged landscape characterized by hills, caves, and springs. Prolonged erosion of these soluble rocks has produced extensive karst features, including sinkholes and underground rivers.Great PlainsfarmingThe lack of other major events left the terrain relatively level; as with the Southeastern U.S./Atlantic Seaboard (see above), the cause of the landscape here is erosion of the Rocky Mountains, with the sediments carried by rivers towards the Mississippi basin and creating a flat, even landscape. Areas were historically shaped by either herds of bison or indigenous agriculture, both limiting the growth of forests. "Farming" is likely a reference to the more recent mix of large-scale crop farming (especially staples like wheat and corn) and herding (bison replaced by cattle). European plowing techniques unsuited for the dry plains ultimately resulted in the Dust Bowl, a period of intense erosion and dust storms which reshaped the landscape, and as a response led to the Great Plains Shelterbelt.Central Idaho / Yellowstonea supervolcanoThe Snake River Plain is an area of high-elevation flat plain in the otherwise contiguous Rocky Mountains. It was formed by the movement of the continental plate over the Yellowstone Hotspot.American West surrounding Idaho / Yellowstonegeology3162: Heart MountainImmediately off of West coast up to the Four CornersvolcanoesA combination of various volcanic fields of different origins, including Cascade Volcanoes in the Pacific Northwest, Albuquerque volcanic field in New Mexico, San Francisco volcanic field in Arizona, and San Juan volcanic field in Colorado.Eastern WashingtonmegafloodsMost likely a reference to the Missoula floods and the Bonneville flood, a series of floods caused by glacial ice dam failures causing massive lakes to flood large regions of present-day eastern Washington. These floods actually continued all the way to the Pacific Ocean, altering the shape of the Columbia River Gorge and flooding much of the Willamette River in western Oregon. The comic may have simplified these to avoid bisecting the adjacent zones along the coast.West Coasta plate tectonic speedrunMost likely a reference to the significant tectonic activity on the western coast of the US, caused by the collisions of the Juan de Fuca plate, Pacific plate, and the North American plate, as part of the Ring of Fire.Southwest Desertwater and timeThe sedimentary rock layers exposed in the geology of the Grand Canyon area range in age from about 200 million to nearly 2 billion years old. Uplift of the region started about 75 million years ago during the mountain-building event creating the Rocky Mountains. The opening of the Gulf of California around 6 million years ago enabled a large river to cut its way northeast from the gulf. The new river captured the older drainage to form the ancestral Colorado River, which started to form the Grand Canyon. Wetter climates from ice ages starting 2 million years ago greatly increased excavation of the Grand Canyon, which was nearly as deep 1.2 million years ago as it is now.Northern AlaskageologyNorthern Alaska geology is dominated by the Brooks Range (a major Paleozoic mountain belt) and the Arctic Slope sedimentary basin, containing rich Paleozoic-Mesozoic rock sequences. The region is part of the Arctic Alaska–Chukotka Microplate, shaped by Mesozoic tectonic shifts, including the Arctic Ocean opening and the Brooks Range uplift.Aleutian IslandsvolcanoesThe Aleutian Islands are a continuation of the Alaskan Aleutian Range, and form part of the Ring of Fire. Most of the islands in the chain bear signs of being formed by volcanoes, and many volcanic cones still exist on the islands today.Southeast AlaskaglaciersThis part of Alaska (including Glacier Bay National Park and Preserve) and western Canada has many glaciers that are still carving the landscape.Hawaiian island chainvolcanoesHawaii, including the Northwest Hawaiian Islands, and seamounts northwest of it were formed by a tectonic plate moving over a hotspot, with volcanoes erupting and forming land as it went. Volcanic fog from the three active volcanoes on the Big Island can often be seen on neighboring islands.Features of each state, alphabeticallyAlabama: continents colliding, farming, riversAlaska: geology, glaciers, volcanoesArizona: water and time, volcanoesArkansas: geology, farming, riversCalifornia: a plate tectonics speedrun, volcanoes, water and timeColorado: volcanoes, geology, farmingConnecticut: glaciersDelaware: farmingDistrict of Columbia: either farming or plates collidingFlorida: farming, ongoing disputes between limestone and waterGeorgia: continents colliding, farmingHawaii: volcanoesIdaho: a super volcano, geologyIllinois: glaciers, riversIndiana: glaciers, riversIowa: glaciers, farming, riversKansas: farmingKentucky: rivers, continents collidingLouisiana: farming, riversMaine: glaciersMaryland: plates colliding, farmingMassachusetts: glaciersMichigan: glaciersMinnesota: glaciers, farming, riversMississippi: farming, riversMissouri: farming, geology, riversMontana: geology, glaciersNebraska: farmingNevada: volcanoes, geology, water and timeNew Hampshire: glaciersNew Jersey: glaciers, farmingNew Mexico: volcanoes, geology, water and time, farmingNew York: glaciers, ???, continents collidingNorth Carolina: continents colliding, farmingNorth Dakota: glaciers, farmingOhio: glaciers, riversOklahoma: farming, geologyOregon: a plate tectonics speedrun, volcanoes, megafloods, a supervolcano, geologyPennsylvania: glaciers, rivers, continents colliding, farmingRhode Island: glaciersSouth Carolina: continents colliding, farmingSouth Dakota: glaciers, farmingTennessee: continents colliding, riversTexas: farming, geology, water and timeUtah: geology, volcanoesVermont: glaciersVirginia: continents colliding, farmingWashington: megafloods, a plate tectonics speedrunWest Virginia: rivers, continents collidingWisconsin: glaciers, riversWyoming: a supervolcano, geology, farmingMore XKCD maps:8 Really Bad Map ProjectionsThe World According to Americans (Who Really Know Their Geography)How To “Improve” The Map of The United States By Cleaning Up Some State BordersHow To Date An Undated World MapWhat Would Happen If You Pulled A 10m Plug In The Mariana TrenchAll The Land In Our Solar SystemMap Projections & What They Say About YouNow Time Map From XKCD 1335You can buy Randall Munroe’s books here:What If?What If? 2How To: Absurd Scientific Advice for Common Real-World ProblemsThing Explainer: Complicated Stuff in Simple Wordsxkcd: volume 0What do you think?