The long, narrow, and rugged Malay Peninsula extends to the south and southwest from Myanmar and Thailand. The Malaysian portion of it is about 500 miles (800 km) long and—at its broadest east-west axis—about 200 miles (320 km) wide. About half of Peninsular Malaysia is covered by granite and other igneous rocks, one-third is covered by stratified rocks older than the granite, and the remainder is...