Hub pages concentrate authority within a topic
A topical cluster is a content structure where a authoritative hub page (e.g., 'The Complete Guide to Home Insulation') links to 10-30 spoke pages covering sub-topics (types of insulation, R-value ratings, installation methods, cost comparisons). Each spoke links back to the hub. This bidirectional linking concentrates authority: search engines infer that the hub is the most authoritative page on insulation because it links to all sub-topics and receives links from all of them.
The density of internal links on a topic signals topical depth. A site with 50 interconnected pages about insulation appears more authoritative on insulation than a competitor with 5 scattered pages about insulation.
Building and measuring topical depth
Identify your core topics (the 5-10 areas your domain should dominate) and build spokes systematically: if insulation is core, create spokes for fiberglass, cellulose, spray foam, cost comparison, R-value, building codes, regional requirements. Internal linking should follow the cluster structure: from hub to all spokes, from each spoke to the hub and 2-3 related spokes. This level of interconnection does not burden users (hidden in sidebars, related articles, topic menus) but signals topical authority to crawlers. Measuring: use internal link analysis tools to visualize your clusters; a well-structured topic should show a star pattern (hub in center, spokes radiating outward).