#geomorphology

Source picture and information from Geología Online

🌍 What do the Himalayas, Greenland, and the Trans-Mexican Volcanic Belt have in common? ⛰️ Although they are separated by thousands of kilometers and have very different landscapes, they all reveal the same phenomenon: the Earth is never completely still. 🌎 Beneath our feet, the Earth's crust constantly sinks, rebounds, and readjusts to maintain equilibrium. ⚖️ This process is known as isostasy.

⛰️ The Himalayas continue to rise due to the collision between the Indian and Eurasian tectonic plates.

❄️ Greenland experiences isostatic rebound because the weight of the glacial ice gradually decreases.

🌋 And the Trans-Mexican Volcanic Belt reflects the internal dynamism of the crust associated with volcanism and tectonic movements.

The tsunami that struck an Alaskan fjord at 5:26 a.m. in 2025 sloshed higher than the height of the top floor of One World Trade Center in NY. It reached 1,578 ft (481 m) up the slopes of the fjord, making it the 2nd-highest tsunami ever recorded. It would have easily washed over the World Trade Center had it not been for its spire. The wave formed a seiche, which is a standing wave that sloshed back & forth in the fjord for over a day. This is unlike a tsunami that moves. Think of it like a giant, natural bathtub slosh that rocks back & forth at the bathtub's own frequency. Because the fjord is long, narrow, enclosed & steep-walled, it formed the perfect geological conditions for a seiche. This was only the 2nd time such a seiche has been recorded.

The cause of the tsunami was a massive landslide that dropped 2.1 billion cubic feet (60 million cubic meters) of rock into the water. Fortunately, no one was hurt or killed by the tsunami because no one was in the fjord at the time. A tour boat had been there 12 hours earlier; if the timing had been different, the casualty count could have been catastrophic. In fact, no one saw or heard the wave, but satellite images & seismic data confirmed its occurrence. The only tsunami bigger than the Juneau one was another Alaskan tsunami, which holds the record for the largest tsunami ever, in 1958 in Lituya, which reached 1,720 ft (524 m) & was also triggered by a massive rockfall. That tsunami wave obliterated a forest on the opposite slope, & 2 people in a fishing boat were killed. The reason Alaska is home to such monsters is that rapid glacier retreat removes structural support from steep slopes. Their deep fjords allow huge water displacement, & their steep walls amplify runup. Alaska's sparse population means such events often go unnoticed. But just as if a tree falls in a forest & nobody's around to hear it, it does not mean it doesn't (or didn't) occur.