The 6.0-magnitude earthquake that jolted parts of Indonesia today served as a reminder of just how active the seemingly-solid ground beneath us can be. And these reminders have become increasingly frequent. On average, the world only sees one or two earthquakes per month that are 6.5-magnitude or higher.   But April produced a higher-than-normal number of the major seismic events, as revealed in this incredible time-lapse video.   According to the Pacific Tsunami Warning Center (PTWC), which issues alerts for tsunamis, there were 13 major earthquakes in April. Five were higher than 7.8, which prompted tsunami warnings. Moderate-to-large earthquakes are less common, but last month was ‘easily a record for this institution,’ according to the PTWC. The time-lapse takes you on a journey of all recorded large and medium-sized earthquakes that took place from January through to April of this year. More