# Are there any mountains/volcanoes steeper than Tharsis Tholus?

Although Olympus Mons is the tallest mountain in the solar system, its slope is so gradual that the peak cannot be seen from the plain; it is hidden by the planet's curvature (flank slope = 5.2°). The answer to this question suggest Tharsis Tholus with average flank slope of 10° followed by Ceraunius Tholus with average flank slope 9°. Tharsis Tholus is considered one of the steepest volcanoes, so are there any mountain/volcanoes steeper than Tharsis Tholus?

I searched for a bit and found Boösaule Montes which is the tallest mountain in Io. The mountain has an irregular morphology, with a relatively gentle slope throughout much of the mountain except for an abrupt scarp on the peak's southeastern margin. According to Schenk et al. 2001, this scarp has a height of approximately 15 km and a slope of 40°. But, I am not sure if this is to be considered as "average flank slope" as it is only steeper on one side.

• I have collected 103 data to conclude the answer, I will let you know soon Dec 22, 2021 at 11:06
• How exactly do you define steepness? Where is the base of a mountain or the upper rim and start of base of a canyon? Do you consider maximum values? Average (if so what is averaged and how (median, mean,...)? Dec 22, 2021 at 14:43
• @planetmaker its as simple as tangent in trig, (not going deep into it) Dec 22, 2021 at 14:48
• @Ishwaran Let me rephrase: Consider a mountain the shape of a perfect half-sphere. How steep is it? 90°? 45°? $<dy/dx> = \frac{2}{\pi} \int_0^\{pi/2} cos(x) dx$? Something else? Dec 22, 2021 at 14:58
• @uhoh there are two ranges with high peaks, one is tenzing montes range and other one is hillary montes range, I will explain those in the question since it needs some work Dec 23, 2021 at 4:06