Moeraki Boulders (IMAGE) Nagoya University Caption Gigantic concretions formed in mudstone on New Zealand's Moeraki coast; about 50 million years old. The present research shows that even concretions of this size formed very rapidly, within several decades. Credit Hidekazu Yoshida Usage Restrictions with credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.