Sea Fossils Near the Sky: How India Met Asia

A Video Call From the Roof of the World

1Once a month, the astronomy club at Fairmont Middle School meets after dark at the town observatory. This month, club advisor Mr. Florian Abara set up a video call with Dr. Tsering Dolkar, an astronomer at a telescope about 4,500 m high in the Himalaya, the tallest mountains on Earth. Observatories are built that high because there is less air above them to blur the stars. Club member Keziah Morrow asked why the mountains are there at all, and Dr. Dolkar, who collects rocks and fossils on her days off, held up a gray rock full of fossil shells.

2"Fossils like these turn up all over the high Himalaya," she said. Limestone near the summit of Mount Everest, 8,849 m above sea level, holds fossils of trilobites and sea lilies, animals that lived on shallow sea floors. Dr. Dolkar then described the rocks a traveler sees on a road that runs north from the hot plains of India, across the mountains and into Tibet (Table 1).

3North of the highest peaks lies a long valley with a belt of dark rock called ophiolite. It is made of basalt with layers of fine mud on top, holding the tiny shells of plankton that live in the open ocean. Rock just like it forms today on the deep ocean floor. Farther north, in southern Tibet, a belt of granite and old volcanic rock runs for more than 1,000 km. Today, chains of volcanoes like this form above ocean trenches, where ocean floor sinks beneath another plate and melts deep below, feeding magma to the surface.

4Dr. Dolkar's observatory also has a GPS receiver. It uses signals from satellites to measure the station's position to within a few millimeters. Comparing it with a GPS station far to the north in Asia shows how the distance between them changes (Table 2). Small and large earthquakes shake the Himalaya often.