Lava flow mapping was conducted on a north-south transect of Olympus Mons using the European Space Agency's Mars Express High Resolution Stereo Camera (HRSC) image H0037. The HRSC image was coregistered to Mars Orbiter Laser Altimeter, Thermal Emission Imaging System, and Mars Orbiter Camera data, enabling lava flow structures to be differentiated and mapped consistently across the shield. Because different structures develop as a result of different effusive conditions, their abundance and distribution provide insight into the eruptive history of a shield volcano. Results show that lava channels are the dominant flow structure, whereas tabular sheets are most common beyond the basal scarp. A hummocky unit dominates the summit area and likely represents a combination of (1) volcanic lava flows, (2) pyroclastic deposits, (3) a dust mantle, and (4) frozen volatiles, all of which have been suggested to exist on Olympus Mons in the past. Lava fans are typically associated with lava tubes, indicating that they represent tube outbreaks as was previously suggested as one possible formation mechanism. No vents were identified, suggesting that major rift zones have not developed on the north or south flank. Younger channel-fed flows typically embay older tube-related flows, which they outnumber by a ratio of 5:1. Therefore Olympus Mons likely experienced a change in eruptive style from longer-lived, stable, tube-forming eruptions to shorter-lived, less stable, channel-forming eruptions in the late Amazonian. A similar trend exists for the Hawaiian volcanoes in which a decrease in the magma production rate drives a change to dominantly channel forming eruptions associated with increased shield age.