Uplifts on Venus and Earth: A Principal Component Analysis

Abstract:

Principal component analysis (PCA) offers a quantitative approach for comparison of topographic profiles. We have previously compared simple shapes of topographic profiles of rifts and uplifts on Venus and Earth. Although yielding some interesting results, these studies were more qualitative than quantitative. We address this by applying PCA to sets of topographic profiles on the two planets. Doing so yields not only groupings of like features in what we call “PC-space," but also the actual shapes of principal component profiles. PC-space consists of a modified ternary diagram showing the relative contributions of the three strongest principal components derived from a particular data set. The first PC profile generally shows a simple broad uplift, while profiles 2 and 3 display more complexity, which we attribute to lithospheric response to loading. Regardless of size of data set, the top three components account for about 95% of the shape of a feature’s profile, so we concentrate our analysis on these three components.

We first look at a data set with several forms of uplift – mid-ocean ridges and continental rifts, and continental and oceanic hotspots on Earth, and chasmata and regiones from Venus. Subsets based on the groupings from this original data set are examined. Specifically, the hotspot data set is tested looking at potential differences between oceanic and continental, and Types 1, 2, and 3 as defined by Courtillot. We look for correlations between terrestrial features and venusian chasmata and regiones. The effect of spreading rate on mid-ocean ridge topography is examined and compared to chasmata.