Explore Patagonia Puerto Madryn Península Valdés Trelew and Gaiman: the Welsh heartland Punta Tombo and Cabo Dos Bahías The coast of Santa Cruz Province Río Gallegos El Calafate Glaciar Perito Moreno El Chaltén The Fitz Roy sector of Parque Nacional Los Glaciares Parque Nacional Perito Moreno Perito Moreno and around Sarmiento and the Bosque Petrificado Share The MONUMENTO NATURAL BOSQUES PETRIFICADOS (aka Jaramillo; free) lies 50 km down a branch road leading west off the RN-3, 80km south of the turn-off to Puerto Deseado. The fossilized tree trunks here are strangely beautiful, especially at sunset, when their jasper-red expanses soak up the glow, as though they’re heating up from within. The sheer magnitude of the trunks is astonishing, too, measuring some 35m long and up to 3m across. The primeval Jurassic forest grew here 150 million years ago – 60 million years before the Andean cordillera was forced up, forming the rain barrier that has such a dramatic effect on the scenery we know now. In Jurassic times, this area was still swept by moisture-laden winds from the Pacific, allowing the growth of araucaria trees. A cataclysmic blast from an unidentified volcano flattened these colossi and covered the fallen trunks with ash. The wood absorbed silicates in the ash and petrified, later to be revealed when erosion wore down the supervening strata. Surrounding the trunks is a bizarre moonscape of arid basalt meseta, dominated by the 400-metre-tall Cerro Madre e Hija (Mother and Daughter Mount). A two-kilometre trail, littered by shards of fossilized bark as if it were a woodchip path through a garden, leads from the park office past all the most impressive trunks, while the small museum has displays of some fascinating fossils such as the araucaria pinecones.