Turret Arch framed by North Window in Arches National ParkUtahUnited States

Rock legends. Old Rock Day

Today is a day that puts time into perspective. Old Rock Day highlights the vast geological processes that have shaped our world since its earliest eras. In Arches National ParkUtahUnited StatesTurret Arch—seen through North Window—offers a striking reminder: landscapes can take hundreds of millions of years to assemble. The Entrada Sandstone that forms these arches began as shifting dunes and shallow seas long before erosion carved today's shapes. Even sothese formations are relatively young. Most rocks on Earth disappear over time because plate tectonicserosion and volcanism continually recycle the crust. Only the planet's ancient continental shields preserve truly old material. Canada's Acasta Gneissabout 4 billion years oldis the oldest known rock still rooted where it formed.

Old Rock Day also remembers the pioneers of geology. Theophrastus and Pliny the Elder recorded early mineral studieswhile Ulisse Aldrovandi helped establish the term 'geology' in 1603. One hundred and fifty years laterWilliam Smith drew the first geological map. And in 1785James Hutton revealed the Earth's immense ageproviding insights that continue to shape our understanding of the ground beneath our feet.