annum (ka, Ma, Ga)

Time before present. A point of time in the geological past, measured backwards from now.

year (kyr, Myr, Gyr)

A measure of duration, not necessarily age and not necessarily measured from the present time.

examples

1. The fossil is dated to 110±2 Ma.
2. According to zircon dating, the granite crystallised at ~30 Ma.
3. The volcano was erupting intermittently for 10 kyr.
4. The Jurassic period lasted for 56 Myr, starting at 201 Ma and 145 Ma.
5. The Jurassic period lasted for 56 Myr, starting 201 Myr ago and ending 145 Myr ago.

annum (ka, Ma, Ga)

Time before present. A point of time in the geological past, measured backwards from now. Often, “now” is defined as the year 1950.

year (kyr, Myr, Gyr)

A measure of duration, not necessarily age and not necessarily measured from the present time.

examples

1. The fossil is dated to 110±2 Ma.
2. According to zircon dating, the granite crystallised at ~30 Ma.
3. The volcano was erupting intermittently for 10 kyr.
4. The Jurassic period lasted for 56 Myr, starting at 201 Ma and 145 Ma.
5. The Jurassic period lasted for 56 Myr, starting 201 Myr ago and ending 145 Myr ago.