In a large pot, heat olive oil over medium heat.
Add onions, carrots, celery, and garlic. Cook until vegetables are tender.
Add split peas, thyme, bay leaf, salt, pepper, and water.
Bring to a boil, then reduce heat and simmer for 1-2 hours, or until split peas are soft.
Remove bay leaf and ham hock from the pot.
Using an immersion blender or a regular blender, blend the soup until smooth.
Serve hot with crusty bread.