AGM?KB 15 July 2023

Dear members & friends, Our talk in August is by Hans Hazebroek, our MNSKB member, who is a Geologist and Naturalist and wrote several books (National parks of Sarawak, Danum Valley, Mulu, Bako, Maliau Basin) as well as geology chapters in 5 books published by UNIMAS. Date: Wednesday 16 August 2023 Time: 7.30 - 9.00 pm Venue: Telang Usan Hotel, Lot 340-345, Ban Hock Road, 93100 Kuching Registration form :https://forms.gle/27FmWV1MZFuCuZ9r9 Only people who registered are welcome since seating is limited to 60 pax. Registration closed on Tuesday 15 Aug. Abstract: In the latter part of the 19th century naturalist and explorer Alfred Russel Wallace was traveling the islands of today’s Malaysia and Indonesia: the Malay Archipelago. This is an immense group of more than 18,000 islands extending over 5000 km from west to east between 95° and 141° E, and crossing the equator from 6° N to 11° S. His extensive fieldwork brought Wallace to the profound insight that the geographical distribution of the hornbills and other animals that he saw was the result of a long and complicated series of geological and organic changes which continuously modify the earth’s crust and the things that live on it. The focus of my talk is to illustrate, with animated geological maps, the gigantic collision of the Australian tectonic plate with the Eurasian plate. Today's Malay Archipelago is the result of this enormous slow-motion crash that took more than 20 million years and is ongoing. GPS measurements indicate that today’s relative motions between tectonic plates in Indonesia vary from 7.7 to as much as 11 centimeters per year. Subduction, when one tectonic plate slides beneath another, triggers earthquakes and causes volcanoes to erupt. Collision between tectonic plates can uplift landmasses such as the entire island of Timor, and build mountain ranges such as the huge mountainous backbone of the island of New Guinea. Following collision, the proximity between the two plates carrying the Australian and Asian floras and faunas respectively creates zones where these floras and faunas merge and interact. The bird and mammal distributions today, from Borneo to Sulawesi, to Maluku, and finally to New Guinea, provide plenty of fascination to further illustrate this in a follow-up talk. Regards, Cynthia Lobato MNSKB Secretariat

Figure 1 Digital elevation model showing topography and bathymetry of the Malaysian - Indonesian island chain: the Malay Archipelago. Between the Malay Peninsula and the islands of Sumatra, Borneo and Java is the shallow sea bed of the Sunda Shelf with water depths considerably less than 200 m. The Sunda Shelf together with much of the lowlands of Sumatra and Borneo is a region that is largely free of earthquakes and is known as Sundaland. Sundaland forms part of the continental core of the region. (Modified after Hall, 2009)