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John M Freedman Profile picture
@DrJohnFreedman
Oct 15, 2020 • 3 tweets • 4 min read • Read on X
KARST formations - works of #geology & works of art. Limestone uplifted from the sea is sculpted for millions of years by water, wind & chemical reactions. Erosion is augmented in the tropics by heat, humidity & vegetation. A classic karst wonderland: #Vietnam’s Ha Long Bay. Image
Below are some other karsts I’ve known and loved.
Clockwise from upper L:
Andaman Sea near Krabi, #Thailand
Yangshuo near #Guilin, China
Vang Vieng in #Laos.
Coron coast and bay in the #Philippines,
Viñales Valley in #Cuba (where the karst outcroppings are called 'mogotes') Image
Another karst wonderland, with a bonus: the area around Puerto Princesa on beautiful Palawan in the #Philippines. Over 5 mi of the Cabayugan River runs through a giant karst cave, much of it navigable by boat from the entry on the turquoise West Philippine Sea. A natural wonder. ImageImageImageImage

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More from @DrJohnFreedman

John M Freedman Profile picture
Dec 31, 2025
HAPPY NEW YEAR TO ALL. And a bit of interesting trivia to celebrate the day: Where is the first inhabited place on Earth to see in the New Year? Answer: Kiritimati, aka Christmas Island, a small atoll in the Line Islands of the Republic of Kiribati. Image
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It's first because the international date line pooches way out in an irregular pattern (since 1995) to encompass all of Kiribati's 3 sprawling island chains: the Line, Gilbert, and Phoenix archipelagoes. The easternmost portion around Kiritimati is the UTC+14 time zone. 2/4 Image
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Kiribati is the only country (and yes, it is a sovereign UN Member State) to straddle all 4 hemispheres. It extends a sprawling 2400 miles east to west in the Pacific- more than the distance from Los Angeles to Washington DC. 3/4 Image
Read 4 tweets
John M Freedman Profile picture
Dec 9, 2025
Attendees at my 'Darwin Down Under' presentation are often surprised to find that it was in Australia's Blue Mountains - not in the Galapagos - that the young naturalist had his first heretical thoughts about the origin of species. 1/6 Image
Darwin was amazed and puzzled that the platypus - a creature strangely and profoundly different from the English water shrew - could exist and thrive in the exact same riverine environmental niche. He noted wryly in his diary that one would have to postulate "two creators." 2/6 Image
The platypus is a monotreme (egg-laying mammal) and only the platypus and 4 species of echidnas (egg-laying spiny anteaters) survive in this group of mammals. Exact origin is unknown but the most ancient platypus fossils are from Australia. 3/6 Image
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Read 6 tweets
John M Freedman Profile picture
Dec 9, 2025
Saw these beautiful vivid blue bird eggs (?fallen from a nest) in the rainforest terrain of tropical Queensland today. Only on closer look, they're not eggs. What are they? Image
They are the fruit of the Blue Marble Tree, Elaeocarpus angustifolius, also known as blue quandong, native to Australia, India and SE Asia. The beautiful blue color is not due to pigments as in other fruits such as blueberries or Concord grapes or plums.Image
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It's a rare example of structural coloration in fruits: The fruit’s epidermis contains tiny microfibrils arranged in a helical structure that selectively reflects and scatters blue wavelengths. The color remains vivid even in dried specimens. More here: mpikg.mpg.de/6832899/struct…
Read 4 tweets
John M Freedman Profile picture
Dec 9, 2025
I took these photos in northern Queensland today to illustrate a point about the koala's opposable thumb(s) in my 'Marsupials & Monotremes' forum. So here goes: Is it true that koalas are the only non-primate with an opposable thumb? Image
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Yes indeed. They actually have 2 opposable digits - a true thumb and an opposable 2nd digit as well, designed for grasping eucalyptus branches. They also have remarkably human-like fingerprints! - likely to help grasp the smooth leaves they feed on. Image
With respect to opposable thumbs, you might hear that possums and pandas have opposable thumbs - not true. The possum has an opposable toe (hallux), not thumb (pollex). The panda has a modified wrist bone (radial sesamoid) for grasping, but the actual thumb is non-opposable. Image
Read 6 tweets
John M Freedman Profile picture
Dec 8, 2025
On this day of solemn tribute to the fallen at Pearl Harbor I want to share one of the key points I make in my 'Epic History of Japan' lecture series. Specifically: Is there truth to the (conspiracy) theory that FDR knew and permitted the attack? Image
A careful review of the evidence does not support the theory that he knew. What he did know - as did both the U.S. and Japanese governments and militaries - is that war was inevitable and coming very soon. The idea that a Japanese attack itself was a surprise is fictitious. 2/8
The oil embargo against Japan in August 1941 was an existential blow to Imperial Japan if left unopposed. Japanese Ambassador Nomura in Washington DC made it clear in November 1941 that war was coming if the embargo was not lifted. 3/8 Image
Read 8 tweets
John M Freedman Profile picture
Dec 6, 2025
The Battle of the Coral Sea, May 4-8, 1942, was a pivotal event in the Pacific War. It was the first time Japanese momentum was stopped, it saved Australia from an isolating blockade or worse, it ushered in a new age of carrier warfare, and it set the stage for the Allies' definitive victory at Midway. 1/6Image
The Battle would thwart the Japanese plan to take Port Moresby in New Guinea, on Australia's doorstep. Aircraft carriers would battle each other via their aircraft without ever directly sighting each other - a first in naval history. 2/6 Image
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The US would lose the venerable 'Lady Lex' (whose wreckage was found by the late Paul Allen in 2018) and the more nimble USS Yorktown would sustain serious damage but make it back to Pearl Harbor for rapid repairs. 3/6 Image
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Read 6 tweets

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