We consider the problem of efficient blind parameter estimation in terahertz (THz)-band ultra-massive multiple-input multiple-output (UM-MIMO) systems. UM-MIMO antenna arrays are crucial to overcoming the distance problem in THz communications. Following recent advancements in THz transceiver design, such arrays are intrinsically compact and reconfigurable. We propose dynamically tuning the modulation types, operating frequencies, and indices of transmitting antenna elements for efficient resource utilization in THz UM-MIMO systems. Furthermore, we propose THz-specific signal processing techniques at the receiver side for blindly detecting the transmission parameters. In particular, we propose a low-complexity antenna index, frequency index, modulation mode, and modulation type detectors, and we study the complexity and performance tradeoffs of the proposed schemes.