The morphology of lava flows can indicate properties of the lava when molten, such as its rheology and flow volume. Together, these properties can provide clues to the lava's composition and eruption rates. For example, lava tubes on Earth only form in lavas of basaltic composition. Silica-rich lavas such as andesite are too viscous for tubes to form. Early quantitative analysis of Alba's lava flows indicated that the lavas had low yield strength and viscosity and were erupted at very high rates. Alba's unusually low profile suggested to some that extremely fluid lavas were involved in the volcano's construction, perhaps komatiites, which are primitive ultramafic lavas that form at very high temperatures. However, more recent work on the tube- and channel-fed flows indicates lava viscosities within the range of typical basalts (between 100 and 1 million Pa s−1). Calculated flow rates are also lower than originally thought, ranging from 10 to 1.3 million m3 per second. The lower range of eruption rates for Alba Mons is within the